Islam teaches that shirk (Arabic: ???? širk) is the sin of idolatry or polytheism, i.e. the deification or worship of anyone or anything other than the singular God, or more literally the establishment of “partners” placed beside God. Within Islam, shirk is an unforgivable crime; God may forgive any sin except shirk.

According to this Islamic scholar, “Saying ‘Merry Christmas’ is worse than fornication or killing someone.”

“To our Muslim readers: We (Christians) worship one God, who has manifested Himself in Three Persons. One Yahweh, one God, Three Persons. No association of anything created or non-eternal. No married gods, no wives or consorts (contra Q. 6:101). Three co-equal and co-eternal Persons sharing fully the one, indivisible being of God. While the Qur’an attempts to identify this as shirk, the author of the Qur’an clearly did not understand the doctrine he was seeking to deny.” – Dr. James White