The Holy Quran, Surah Al-Nisa’ 4:171
O People of the Book! Commit no excesses in your religion: Nor say of Allah aught but the truth. Christ Jesus the son of Mary was (no more than) a Messenger of Allah, and His Word, which He bestowed on Mary, and a Spirit proceeding from Him: so believe in Allah and His Messengers. Say not “Trinity” : desist: it will be better for you: for Allah is One God: Glory be to Him: (far exalted is He) above having a son. To Him belong all things in the heavens and on earth. And enough is Allah as a Disposer of affairs.