Greeting the Christians during their feasts

Q: What is the ruling on greeting the Christians during their feasts? I have a maternal uncle who exchanges greetings with his Christian neighbor when either of them has a wedding, a feast, or any other occasion? Is it permissible for a Muslim (Part No. 3; Page No. 436) to greet a Christian and vice versa on the occasions of festivals and wedding parties? Please give me a Fatwa (legal opinion issued by a qualified Muslim scholar), may Allah reward you with the best.

A: It is not permissible for a Muslim to greet the Christians during their festivals, since this implies cooperation in sin, from which we are forbidden. Allah (Exalted be He) says: ...but do not help one another in sin and transgression. This also implies endearment to them, seeking their affection, and expressing that we are content with them and their rites, which is not permissible. Rather, it is Wajib (obligatory) to display enmity and hatred towards them, since they oppose Allah (Glorified and Exalted be He), associate others with Him, and claim that He (Glorified be He) has a wife and a child. Allah (Exalted be He) says: You (O Muhammad صلى الله عليه وسلم) will not find any people who believe in Allâh and the Last Day, making friendship with those who oppose Allâh and His Messenger (Muhammad صلى الله عليه وسلم), even though they were their fathers or their sons or their brothers or their kindred (people). For such He has written Faith in their hearts, and strengthened them with Rûh (proofs, light and true guidance) from Himself. And: Indeed there has been an excellent example for you in Ibrâhîm (Abraham) and those with him, when they said to their people: "Verily, we are free from you and whatever you worship besides Allâh: we have rejected you, and there has started between us and you hostility and hatred for ever until you believe in Allâh Alone" May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.