What is the ruling regarding congratulating non-Muslims on their holidays and celebrations?
It is not permissible for the Muslims to congratulate the Christians for their holidays and celebrations because this would be cooperation on that which is sin and transgression. Allah Says (what means): "…And cooperate in righteousness and piety, but do not cooperate in sin and aggression…" [Quran 5: 2]. This also leads to repeated visitation with them, and indicates solicitation of their love and the acceptance of who they are and their rites. This is not permissible. It is an obligation on the Muslim to show them dislike for they oppose Allah and ascribe partners and sons to Him. Allah Says (what means): "You will not find a people who believe in Allah and the Last Day having affection for those who oppose Allah and His Messenger, even if they were their fathers or their sons or their brothers or their kindred…" [Quran 58:22] He Almight also Says: "There has already been for you an excellent pattern in Abraham and those with him, when they said to their people, 'Indeed, we are disassociated from you and from whatever you worship other than Allah. We have denied you, and there has appeared between us and you animosity and hatred forever until you believe in Allah Alone'…" [Quran 60:4]
Allah Knows best.