All Prophets Were Muslim – Al-Quran
[2:135] They say: “Become Jews or Christians if ye would be guided (To salvation).” Say thou: “Nay! (I would rather) the Religion of Abraham the True, and he joined not gods with Allah.”
[2:136] Say ye: “We believe in Allah, and the revelation given to us, and to Abraham, Isma’il, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: We make no difference between one and another of them: And we bow to Allah (in Islam).”
[2:137] So if they believe as ye believe, they are indeed on the right path; but if they turn back, it is they who are in schism; but Allah will suffice thee as against them, and He is the All-Hearing, the All-Knowing.
[2:138] (Our religion is) the Baptism of Allah: And who can baptize better than Allah? And it is He Whom we worship.
[2:139] Say: Will ye dispute with us about Allah, seeing that He is our Lord and your Lord; that we are responsible for our doings and ye for yours; and that We are sincere (in our faith) in Him?
[2:140] Or do ye say that Abraham, Isma’il Isaac, Jacob, and the Tribes were Jews or Christians? Say: Do ye know better than Allah? Ah! who is more unjust than those who conceal the testimony they have from Allah? but Allah is not unmindful of what ye do!