Circumcision, though not mentioned in the Quran, is obligatory in Islam, because of many Hadith narrations which include it as part of how a human being ought to be (Fitra):
Sahih al-Bukhari 5891
Narrated Abu Huraira:
I heard the Prophet (ﷺ) saying. "Five practices are characteristics of the Fitra: circumcision, shaving the pubic hair, cutting the moustaches short, clipping the nails, and depilating the hair of the armpits."
The above is also narrated in Sahih al-Bukhari 5889, 6297, Sahih Muslim 257a-b, Sunan an-Nasai 9-11, 5042-44, 5225, Sunan abu-Dawud 4198, Sunan ibn-Majah 292, and Jami at-Tirmidhi 2756.
This circumcision mandate is an especially good example of how Muhammad had absolutely no idea about what the Bible taught, and was not continuing the revelation of the Biblical authors as he claimed (Surah 3:3-4, 5:43-48, 5:68, etc.), but was instead inventing a brand new religion, which was a mishmash of whatever his depraved, carnal, Satanic mind conceived to throw together.
This is because, by carrying on the practice of circumcision, Muhammad demonstrated that he did not understand even the very basics of the purpose of the New Covenant, which makes sense, because the New Covenant began with Christ's death on the cross (Hebrews 9:15-16), which Muhammad rejected (Surah 4:157-158).
One of the things that Christ's death secured us was redemption from all of the carnal ordinances of the Law (Hebrews 9:10), one of which was circumcision:
Galatians 5:1-6, 6:15
1 Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage.
2 Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing.
3 For I testify again to every man that is circumcised, that he is a debtor to do the whole law.
4 Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace.
5 For we through the Spirit wait for the hope of righteousness by faith.
6 For in Jesus Christ neither circumcision availeth any thing, nor uncircumcision; but faith which worketh by love.
15 For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature.
As can be seen above, Muhammad, with his reinstitution of this fulfilled law, has made Muslims debtors to keep the entire Old Testament Law - and they've all already failed miserably (Galatians 2:16, 3:11).
Muhammad didn't understand the symbol of circumcision, nor its New Testament fulfillment, which had to do with picturing the spiritual circumcision of New Birth (John 3:3) in distinction from the flesh (Romans 7:22-25), and the unification of all believers - regardless of whether they were Jew or Gentile - in a single body (Galatians 3:28):
Colossians 2:10-11
10 And ye are complete in him, which is the head of all principality and power:
11 In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ:
Philippians 3:2-3
2 Beware of dogs, beware of evil workers, beware of the concision.
3 For we are the circumcision, which worship God in the spirit, and rejoice in Christ Jesus, and have no confidence in the flesh.
The fulfillment of the symbol of circumcision described above in the New Testament gives the practice, which began with God's covenant to Abraham (Genesis 17:10-14), spiritual and theological significance. Circumcision in Islam is hijacked, and relegated to some aesthetic purpose alongside other grooming practices, because the dumbbell false prophet Muhammad didn't understand any aspect of the symbol at any point in time.
The practice of "female circumcision" is practiced in Islam, because Muhammad described intercourse as "the circumcised meeting the circumcised":
Jami at-Tirmidhi 109
Aishah narrated that:
The Prophet said: "When the circumcised meets the circumcised then Ghusl is required."
The above narration is also found in Jami at-Tirmidhi 108, and Sunan ibn-Majah 608
There is also another Sahih narration in which Muhammad instructs a practitioner of "female circumcision" how best to perform the practice, obviously, implicitly giving it approval:
Sunan abu-Dawud 5271
Narrated Umm Atiyyah al-Ansariyyah:
A woman used to perform circumcision in Medina. The Prophet (ﷺ) said to her: Do not cut severely, as that is better for a woman and more desirable for a husband.
What does he say above? "Don't ever do that, at all"? No, rather, he tells her how to do it.
Therefore, the Arabian false religion of Islam is responsible for perpetuating the Pagan, unbiblical, Satanic practice of "female circumcision", the name of which is obviously ridiculous, as there is nothing with a "circumference" on a woman to be able to "circumcise" in the same manner as a foreskin on a male, the lack of which, in the final estimation, is almost inconsequential to a man's life.
Instead, this is more properly called female genital mutilation, as what's being cut is not inconsequential at all, and is something God never told anyone to do, ever.
Muhammad also taught that Abraham, the first man that God told to circumcise himself, circumcised himself at 80 years old:
Sahih Muslim 2370
Abu Huraira reported Allah's Messenger (ﷺ) as having said that:
Ibrahim (as) circumcised himself with the help of an adze when he was eighty years old.
This is also narrated in Sahih al-Bukhari 3356.
Of course, as with every single Bible story Muhammad attempted to tell in his career as a false prophet, he got it wrong. Abraham was not 80 years old when he was circumcised, he was 99 years old:
Genesis 17:24
24 And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.
Muhammad literally could not relay any Bible story, no matter how simple, accurately. He lied consistently, about everything, everywhere he went.
The false prophet Muhammad was completely ignorant of the original God-ordained meaning of circumcision, and consequently, it should be no surprise that his teaching on the practice is utterly opposed to what God actually revealed in His Word, which the lying false prophet Muhammad claimed to affirm.