FGM is mandated in Islamic law: “Circumcision is obligatory (for every male and female) (by cutting off the piece of skin on the glans of the penis of the male, but circumcision of the female is by cutting out the bazr ‘clitoris’ [this is called khufaadh ‘female circumcision’]).” — Umdat al-Salik e4.3, translated by Mark Durie, The Third Choice, p. 64

Why is it obligatory? Because Muhammad is held to have said so: “Abu al- Malih ibn Usama’s father relates that the Prophet said: ‘Circumcision is a law for men and a preservation of honour for women.’” — Ahmad Ibn Hanbal 5:75

“Narrated Umm Atiyyah al-Ansariyyah: A woman used to perform circumcision in Medina. The Prophet (peace be upon him) said to her: ‘Do not cut severely as that is better for a woman and more desirable for a husband.’” — Abu Dawud 41:5251

That hadith is classified as weak, but this one is classified as sahih (reliable): “Aishah narrated: ‘When the circumcised meets the circumcised, then indeed Ghusl is required. Myself and Allah’s Messenger did that, so we performed Ghusl.’” — Jami` at-Tirmidhi 108

If Muhammad had the genitals of his favorite wife, Aisha, mutilated, that is a strong endorsement of the practice from the man who is an “excellent example” (Qur’an 33:21) for Muslims.

Why does it matter whether or not FGM is Islamic? Because the practice will never be eradicated if its root causes are not confronted. As long as those Muslims continue to believe that Allah and Muhammad want it done, for some that will override all other considerations.

“Girl, 12, dies after undergoing female genital mutilation in Egypt,” by Jimmy Nsubuga, Metro News, January 31, 2020 (thanks to The Religion of Peace)