Shaykh ul-Islam Ibn Taymiyyah, in his treatise, "al-Waasitah bayn al-Haqq wal-Khalq", (Intermediation Between al-Haqq [Allaah] and the Creation) provides an excellent explanation of this subject. Before we quote the passage from this treatise, the following background information should be understood.

Background

Just like the mulk (dominion) belongs to Allaah alone, and just like izzah (might, honour) belongs to Allaah alone, and just like Allaah alone is the dispenser of rahmah (mercy), and just like Allaah alone is the source of barakah (blessing, increase, growth) and so on, and just like none grants maghfirah (forgiveness) except Allaah alone, then likewise, to Allaah alone belongs all shafaa'ah ( intercession ) - and these meanings are found in the Qur'an.

Allaah says in the Qur'an, in relation to shafaa'ah ( intercession ):

قُل لِّلَّهِ الشَّفَاعَةُ جَمِيعًا لَّهُ مُلْكُ السَّمَاوَاتِ وَالْأَرْضِ ثُمَّ إِلَيْهِ تُرْجَعُونَ قُل لِّلَّهِ الشَّفَاعَةُ جَمِيعًا لَّهُ مُلْكُ السَّمَاوَاتِ وَالْأَرْضِ ثُمَّ إِلَيْهِ تُرْجَعُونَ

Say: "To Allah belongs all intercession . His is the Sovereignty of the heavens and the earth, then to Him you shall be brought back." (Az-Zumar 39:44)

Just like the dominion, sovereignty belongs to Allaah alone, likewise, the intercession belongs to Allaah alone. What this means is that there is no intercession except with His permission, and there is no intercession except for the one with whom He is pleased. This is the meaning of "to Allaah belongs all intercession". And both these conditions are found in the following verse:

يَوْمَئِذٍ لَّا تَنفَعُ الشَّفَاعَةُ إِلَّا مَنْ أَذِنَ لَهُ الرَّحْمَنُ وَرَضِيَ لَهُ قَوْلًا يَوْمَئِذٍ لَّا تَنفَعُ الشَّفَاعَةُ إِلَّا مَنْ أَذِنَ لَهُ الرَّحْمَنُ وَرَضِيَ لَهُ قَوْلًا

On that day no intercession shall avail, except the one for whom the Most Beneficent (Allah) has given permission and whose word is acceptable to Him. (Ta-Ha 20:109)

And these two conditions are mentioned in other verses too ( Baqarah 2:255 , Anbiyaa 21:28 ). When this is established, it follows that the asking of intercession is only from Allaah, just like the asking of barakah (blessing) is only from Allaah, and the asking of rahmah (mercy) is only from Allah, and the asking of maghfirah (forgiveness) is only from Allaah, and the asking of izzah (glory, honour) is only from Allaah. Consider the following verse:

قُلِ اللَّهُمَّ مَالِكَ الْمُلْكِ تُؤْتِي الْمُلْكَ مَن تَشَاء وَتَنزِعُ الْمُلْكَ مِمَّن تَشَاء وَتُعِزُّ مَن تَشَاء وَتُذِلُّ مَن تَشَاء بِيَدِكَ الْخَيْرُ إِنَّكَ عَلَىَ كُلِّ شَيْءٍ قَدِيرٌ قُلِ اللَّهُمَّ مَالِكَ الْمُلْكِ تُؤْتِي الْمُلْكَ مَن تَشَاء وَتَنزِعُ الْمُلْكَ مِمَّن تَشَاء وَتُعِزُّ مَن تَشَاء وَتُذِلُّ مَن تَشَاء بِيَدِكَ الْخَيْرُ إِنَّكَ عَلَىَ كُلِّ شَيْءٍ قَدِيرٌ

Say (O Muhammad): "O Allah! Possessor of the kingdom, You give the kingdom (mulk) to whom You will, and You take the kingdom from whom You will, and You endue with honour whom You will, and You humiliate whom You will. In Your Hand is the good. Verily, You are Able to do all things. (Aali Imran 3:26)

In this verse, Allaah establishes that He is the "Owner" of the dominion (mulk), then He says that He gives dominion (mulk) to whomever He wills and removes it from whomever He wills. And also consider the following verse:

مَن كَانَ يُرِيدُ الْعِزَّةَ فَلِلَّهِ الْعِزَّةُ جَمِيعًا مَن كَانَ يُرِيدُ الْعِزَّةَ فَلِلَّهِ الْعِزَّةُ جَمِيعًا

Whosoever desires izzah (honour, power and glory) then to Allah belong all honour, power and glory (Fatir 35:10)

So all izzah (might, honour, glory) belongs to Allaah and (from the previous verse) He gives it to whomever He wills and removes it (i.e. humiliates, lowers) from whomever He wills.

When you grasp this with respect to mulk (dominion) and izzah (might, honour, glory) and barakah (blessing) - and all of this is found in the Qur'an, then it is exactly the same with the saying of Allaah:

قُل لِّلَّهِ الشَّفَاعَةُ جَمِيعًا قُل لِّلَّهِ الشَّفَاعَةُ جَمِيعًا

Say: "To Allah belongs all intercession ..." (Az-Zumar 39:44)

As all intercession belongs only to Him alone, then it is asked and sought from Him alone, and it is not asked of those besides Him, since He is the only granter of intercession (shafee') in truth and in reality, and all intercession returns back to Him, and those besides Him have absolutely no say or power or ability in intercession without His permission and pleasure.

And we see in the Qur'an shafaa'ah being negated and also being affirmed. That which is affirmed is the shafaa'ah for which Allaah has granted permission for it to be sought, which is sought from Allaah, and whose recipient He is pleased with. And that which is negated is the requesting of shafaa'ah from others besides Allaah.

Fathoming The Topic of Intercession Now, when we speak of shafaa'ah ( intercession ) and those who seek it and ask of it from others besides Allaah, what does this mean practically? Let us explain. It is known that on the Day of Judgement, the Prophet Muhammad (alayhis salaam) and the Prophets in general, and the Angels and the Righteous, will all intercede for others with Allaah. This is the intercession that these people seek, however they request it by way of calling upon those who are dead from amongst the Prophets, and Righteous. They also request immediate intercession (from those who are dead) which is besides the one being sought for the Hereafter. And in all of this they combine a number of things, firstly , supplicating ( du'a ) upon other than Allaah, (where the supplication is directly to other than Allaah) and secondly , asking them for something in which they have no say, power or ability, which is the intercession that belongs to Allaah alone, since there will be absolutely no intercession on the Day of Judgement except with His permission. It will not be allowed to take place by anyone, and nor accepted for anyone except for he whom Allaah is pleased with. To fathom this further , you should imagine these people invoking the dead and asking them for forgiveness, or asking them for sustenance, or asking them for izzah (might, honour) when all these things belong only to Allaah and lie within his authority alone. And the same with shafaa'ah , there is no difference between them at all, as all belong to Allaah alone. To fathom this even further , imagine the situation where someone goes to a living person and says, "Intercede for me with Allaah on the Day of Judgement", now you know this is wrong, because firstly how do you know that person is going to be in a position to intercede in the first place, secondly, how can that person intercede on the Day of Judgement in the absence of Allaah's permission, [and even the Prophet (Muhammad) will not intercede until after Allaah grants permission], so how then for those less than him - this is challenging Allaah's authority and treating him like the kings of the earth with whom people intercede without their permission. Now, this is regarding a living person, and it becomes worse when you invoke a dead person with the same request. So from this you should understand the great mistake of these people in what they do. When they become attached to others besides Allaah (through the lure of seeking intercession), invoking them, then invocation is such that underlying it or accompanying it are other actions (of the heart) which constitute worship in their own right, such as the type of love, hope, aspiration, reliance and the likes, that is due only to Allaah. So these people, through the route of seeking intercession , open themselves up to committing shirk with Allaah. And indeed, it was in this subtle, step-by-step manner that Iblees misguided many a nation and civilization in the past into worshipping others besides Allaah. Also it is highly recommended that you read this article: False worship and False Religion: Derives From Four Roots Which Have All Been Negated By the Qur'an - (see here)

Once all this is grasped well, we can move and see how this subject is connected to Tawhid (Monotheism), and how the failure to understand this, and to understand the true nature of the associationism ( shirk ) of those rebuked in the Qur'an, leads people to end up giving their devotion and worship to others besides Allaah, upon false and rejected assumptions.

Ibn Taymiyyah on the Affirmed and Rejected Types of intermediaries

The titles are added for making the passage easy to read and follow:

THE SCHOLARS ARE THE INHERITORS OF THE PROPHETS AND THEY ARE intermediaries OF KNOWLEDGE AND ITS DISSEMINATION

Those who affirm people other than the Prophets - such as the shaikhs [scholars] of Knowledge and of the religion - as intermediaries between the Messenger and his Ummah in the sense that they are people who impart knowledge to them (the Ummah), teach them (such knowledge) and correct their conduct and then follow in their way, they are correct in doing so (i.e. considering them intermediaries in this particular manner). When these scholars agree upon a matter, their concensus is an absolute proof. They never unite upon misguidance and if they differ upon any issue they always refer it to Allaah and His Messenger. This is because not a single one of them is free from making mistakes in an absolute manner, rather every persons words can either be accepted or rejected except the words of the Messenger (sallallaahu alaihi wasallam). The Messenger (sallallaahu alaihi wasallam) said: "The scholars are the inheritors of the Prophets and the Prophets do not leave behind dinars or dirhams but they leave behind the knowledge so whoever takes from it then he has acquired a huge fortune." [Abu Daawood]

THE INTERMEDIATION OF SHIRK

There are those who affirm them as being intermediaries between Allaah and His creation in the manner of a barrier which is between a king and his citizens and who raise to Allaah the needs of His creation - such that Allaah guides His servants and gives them sustenance throught their intermediation, the creation asks them and they ask Allaah. This is like the intermediaries between the kings and their people who ask for the needs of the people because they are closer to the kings than the people themselves. So the people ask them courteously, that they should take their request to the king, or thinking that their requesting the intermediaries is more beneficial for them than requesting from the king directly because the intermediaries are closer to the king than the one making the request. Whoever affirms the scholars as intermediaries in such a manner then he is a Kaafir (disbeliever) and a Mushrik (pagan). It is necessary to seek his repentance and if he does not make repentance he must face death. Such people make resemblances for Allaah, they compare the creation with the Creator and set up rivals and equals with Allaah.

THE REJECTED TYPES OF INTERMEDIARIES

There is a refutation of these people within the Qur?aan which is too vast to mention in this treatise. Intermediation between the kings [of this world] and their people occurs in one of three ways: THE FIRST: Informing the king of the situation of the people which the king by himself does not know. Whoever says that Allaah does not know the condition of His servants until some of the angels or the prophets or anyone else informs Him of that he is a Kaafir. Rather He, the One Free from all Imperfections, knows [all the] secrets and what is most hidden. No one can hide anything from Him in the Heavens and the Earth and He is the Hearer, the Seer. He hears the sounds of all the tongues in all the different languages with all the diversity of their requests. Listening to one does not occupy Him from listening to another. Neither does this cause Him to make mistakes and nor is He exhausted by the persistence of the insistent. THE SECOND: When the king is incapable of administering and regulating his people and in repelling his enemies except by helpers who assist Him. He cannot do without these assistants due to his weak position and incapacity. However, Allaah, the One free of all imperfections and limitations is not in need of a helper nor any allies to help Him.Allaah the Exalted said: Say: "Call upon other (gods) whom you fancy, besides Allaah: They have no power,- not the weight of an atom,- in the heavens or on earth: No (sort of) share have they therein, nor is any of them a helper to Allaah." (Sabaa 34:22) And He said: Say: "Praise be to Allaah, who begets no son, and has no partner in (His) dominion: Nor (needs) He any to protect Him from humiliation: and magnify Him for His greatness and glory!" (Israa 17:111) Allaah is the Creator, the Lord and the Owner of everything which is in existence. He is the One free of all needs from that which is besides Him and all that is besides Him is in need of Him in opposition to the kings who are in need of their helpers. In reality such people are their partners in the ownership of their dominion and kingdom. Allaah the Exalted has no partner in His dominion, rather there is none deserving of worship except Allaah alone, without any partners, to Him is the dominion, to Him belongs all Praise and He has power over all things. THE THIRD: When the king does not desire any benefit for his people and showing benevolence and mercy to them except due to an external movement which urges him to do so. The concern of the king for fulfilling the needs of his flock changes either due to his heart being affected by the words of the one who advises, warns him and directs him or due to the fear or aspiration which occurs (in his heart) on account of the words of the one who is directing him However Allaah the Exalted is the Lord and Owner of everything. He is more merciful to His servants than a mother is to her offspring. Everything occurs by His Will, whatever He wills happens and whatever He does not will does not occur. When He sends down benefit for His servants he makes one of them do good towards another by supplicating for him or interceding for him (in a matter of the world) and other such things. Allaah is the Creator of all of that and He is the One who created in the heart of this doer of good, who supplicates and intercedes, the desire to do good, make supplications and intercede. It is not possible that there is anyone in the creation who can compel Him against his will or desire or inform Him about something which He did not know or whom He hopes in or fears. For this reason the Messenger (sallallaahu alaihi wasallam) said: "Let not one of you say: O Allaah! Forgive me if you will, have mercy upon Me if you will. Let him be firm and resolute in the matter for there is none to compel Allaah (to do something)." [Bukhaaree]

The Difference Between the intercession That Belongs to Allaah and That Which is Made With the Kings

As for the interceders who intercede with Allaah, they do not do so except by His permission just like Allaah has said: Who is there to intercede with Him except with Him permission (Baqarah 2:255) And the Exalted also said: And they offer no intercession except for those whom (Allaah) is pleased with (Anbiyaa 21:28) Allaah has also said: Say: "Call upon other (gods) whom you fancy, besides Allaah: They have no power,- not the weight of an atom,- in the heavens or on earth: No (sort of) share have they therein, nor is any of them a helper to Allaah. No intercession can avail in His Presence, except for those for whom He has granted permission. (Sabaa 34:22) Allaah has explained that everyone who is called upon besides Him does not have any possession or share in the dominion and neither is he a helper to Allaah. He also explained that their intercession will not benefit anyone except for whom permission has been granted by Allaah. This is not so in the case of the kings of this world because the one who intercedes with them often has some sort of dominion or power and is sometimes a partner to them in their kingdom. Sometimes he is helps or assists them in the management of their kingdom. And all of these people intercede with the king without the permission of the king. The king sometimes accepts their intercession due to a need he has from them, or due to fear of them, or to reward them for their good conduct towards him and causing benefit to him. The king may even accept the intercession of his wife and son because he is in need of a wife and a son and if they were to turn away from him he would be harmed by that. He also accepts the intercession of his citizens because he fears that if it was not accepted they would not obey him or that they might try to cause him harm. The intercession of people for each other, all of it is of this type. No one accepts intercession except out of fear or hope/aspiration. Allaah the Exalted does not hope in anyone, however, nor does He fear anyone. He is Al-Ghaniy (the One Free of all needs). The Exalted said: Behold! verily to Allaah belong all creatures, in the heavens and on earth. What do they follow who worship as His "partners" other than Allaah? They follow nothing but fancy, and they do nothing but lie. He it is That has made you the night that you may rest therein, and the day to make things visible (to you). Verily in this are signs for those who listen (to His Message). They say: "Allaah has begotten a son!" - Glory be to Him! He is self-sufficient! His are all things in the heavens and on earth! (Yoonus 66-68) Allaah the Exalted said: They serve, besides Allaah, things that hurt them not nor profit them, and they say: "These are our intercessors with Allaah." Say: "Do you indeed inform Allaah of something He knows not, in the heavens or on earth? Glory to Him! and far is He above the partners they ascribe (to Him)!" (Yoonus 10:18) He also said: Why then was no help forthcoming to them from those whom they worshipped as gods, besides Allaah, as a means of access (to Allaah)? Nay, they left them in the lurch: but that was their falsehood and their invention. (Ahqaaf 46:28) He also informs about the pagans who said: We do not worship them except that they may bring us closer to Allaah (Zumar 39:3) And He said: And He does not command you to take the angels and the prophets as lords besides Allaah. Would he command you with Kufr while you are Muslims (Aali Imraan 3:80)

Summary

This topic is a foundational one as it relates to Tawhid, and from the above, it should be clear that intercession ( shafaa'ah ) belongs to Allaah alone , that He alone grants it, and that it should be asked only from Him alone, and that likening Allaah to the kings of the Earth as it relates to how intercession takes place with them, then that is a revilement upon Allaah , and anyone who believes that this is how Allaah operates with respect to His creation has committed kufr, for Allaah is free from all the deficiencies of created beings, lofty and exalted is He from all of that.

However, the opponents of the Prophets and Messengers have their doubts and arguments in this regard and these will be addressed in detail in other articles.