All perfect praise be to Allah, The Lord of the World. I testify that there is none worthy of worship except Allah, and that Muhammad (S.A.W) is His Messenger. We ask Allah to exalt his mention as well as that of his family and all his companions. A Muslim should be thankful to Allah for His great blessings upon him. He Who guided him to the right path. So he should keep on supplicating Allah to make him steadfast on this path which is the path of blessed people and to keeping him away from the path of those who deserve His Anger and of those who went astray.
The non-Muslims spare no efforts to draw the Muslims away from the straight path and to cut their relation with their true religion. Allah says (what means): {Many of the people of the Scripture (Jews and Christians) wish that if they could turn you away as disbelievers after you have believed, out of envy from their own selves, even, after the truth (that Muhammad is Allah’s Messenger) has become manifest unto them. But forgive and overlook, till Allah brings His Command. Verily, Allah is Able to do all things.} [Quran 2:109]
We the Muslims are proud of our religion that was revealed to us by Allah and are thankful that Allah has chosen us for his religion. Allah says (what means): {… This day, I have perfected your religion for you, completed My Favour upon you, and have chosen for you Islam as your religion. …} [Quran 5:3]
It is not permitted for Muslims to participate in the festivals of non-Muslims because it is a kind of cooperation in the disobedience of Allah. Allah says (what means): {…Help you one another in Al-Birr and At-Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression….} [Quran 5:2]. The Prophet said: "Whoever imitates a nation is but one of them." [Abu Daawood]
Celebrating festivals such as Christmas Day, Halloween, Valentine Day, etc. comes under the falsehood that should be avoided. Allah says (what means): {And those who do not bear witness to falsehood, and if they pass by some evil play or evil talk, they pass by it with dignity.} [Quran 25:72]. Many scholars of Qur'an like Ibn Seereen and Mujaahid interpret "falsehood" as the festivals of unbelievers.
Anas reported: "The Prophet Muhammad (S.A.W) came to Madeenah while they had two days they celebrated. The Prophet Muhammad (S.A.W) asked, "What are these two days?" They said, 'These are two days we used to celebrate in our pre Islamic era. The Prophet Muhammad (S.A.W) said: "Allah has replaced them with two better days: 'Eid-Ul-Adhaa and 'Eid-Ul-Fitr." A person came to the Prophet and said: "I have taken a vow to sacrifice a camel at Buwaanah.” The Prophet Muhammad (S.A.W) asked: “Did the place contain any idol worshipped in Jaahiliyyah (pre-Islamic times)?” They (the people) said: “No.” He asked: “Was any pre-Islamic festival observed there?” They replied: “No.” The Prophet Muhammad (S.A.W) said: “Fulfil your vow, for a vow to do an act of disobedience to Allaah must not be fulfilled, neither must one do something over which a human being has no control."
No doubt celebrating such feasts is actually imitating disbelievers. Abdullah Ibn Amr Ibn al-'Aas said: “Whoever celebrates the Persian New Year's Day or their carnival and imitates them till his death he will be resurrected with them on the Day Judgment.”
Therefore, a Muslim is neither allowed to celebrate such festivals nor is he allowed to congratulate non-Muslims for their feasts because congratulating them for their feasts is synonymous of accepting their wrongdoing and disbelief in Allah. It is also accepting their rites and rituals, which are nothing but disbelief.
Imaam Ibn Al-Qayyim reported the consensus of all scholars that congratulate non-Muslims for their religious occasions is forbidden. He said: “As for congratulating the unbelievers for their rituals, it is forbidden according to the agreement of all scholars like congratulating them for their feasts and fast by expressing good wishes: happy feast or enjoy your feast… etc. If the Muslim who says this does not become a disbeliever himself, he, at least, commits a sin as this is the same as congratulating him (a non-Muslim) for his belief in the Trinity, which is a greater sin and much more disliked by Almighty Allah than congratulating him for drinking alcohol or killing a soul or committing fornication or adultery etc.”
Therefore, no Muslim is allowed to participate in the festival celebration of non-Muslims or greet them on this occasion. Know that partially participating in such occasions is enough to involve one in sin even if one does not intend to participate wholly in the celebration.
Finally, if they congratulate us for our feasts, we do not congratulate them for their feast as we are on the right path and they are in error. Allah says (what means): {and whoever seeks a religion other than Islam, it will never be accepted of him and in the Hereafter he will be one of the losers} [Quran 2:85]