‘Alī b. Abī Ṭālib – Allah be pleased with him – said:

Narrate to people what they can understand; do you want Allah and His Messenger to be disbelieved?

Quoted by Al-Bukhārī, Al-Ṣaḥīḥ, Chapter about a person preferring some people with certain knowledge to the exclusion of others.

Ibn Ḥajr said in Fatḥ Al-Bārī, “[In this narration] there is evidence that ambiguous knowledge should not be mentioned amongst the general public.”

Shaykh Muḥammad b. Ṣāliḥ Al-‘Uthaymīn – Allah have mercy on him – explained this very important and often misunderstood point beautifully. After mentioning the narration of ‘Alī, he states:

It is therefore an aspect of wisdom in da’wah (calling others to Allah) that you should not surprise people with things they are not able to comprehend. Rather, you should call them in stages, bit by bit until their minds settle…”

He goes on to say:

“[The statement of ‘Alī] ‘Do you want Allah and His Messenger to be disbelieved?’ is a rhetorical question, posed as a criticism of such behavior. It means: by narrating to people things they cannot understand do you want Allah and His Messenger to be disbelieved? This is because in such cases when you say, “Allah said, and His Messenger said” they will say you have lied if their minds cannot comprehend what you are saying. Here, they are not disbelieving Allah and His Messenger, but they are disbelieving you because of this speech that you have attributed to Allah and His Messenger. Thus they will end up disbelieving Allah and His Messenger – not directly – but by way of the one who transmits this knowledge (i.e. you).

Now if it is said: Should we stop telling people things they cannot understand even if they need to know? The answer is: no, we do not leave this knowledge altogether, but we should tell them in a way that they will be able to understand. This is done by telling them stage by stage, bit by bit until they can accept the speech we want them to know and they can feel comfortable with it. We do not abandon knowledge that people cannot understand and just say ‘this is something they will reject or dislike so we will not speak about it.’

The same is the case with acting upon a Sunnah that people are not used to and which they might find objectionable. We should act by this Sunnah, but only after informing people about it, such that they will be able to accept it and feel comfortable about it.

We learn from this narration (of ‘Alī) that it is important to employ wisdom in calling to Allah, and that it is incumbent upon anyone who calls to Allah to consider the level of understanding of those he is inviting, and that he should put everyone in their proper place.

Majmū’ Fatāwā Ibn ‘Uthaymīn Vol.10 p140.