This aaayah itself praises and commends (those who do not witness falsehood), which has the meaning of urging people to avoid taking part in their festivals and other kinds of falsehood. We understand that it is bad to attend their festivals because they are called al-zoor (falsehood).
It indicates that it is haraam to do this for many reasons, because Allaah has called it al-zoor. Allaah condemns the one who speaks falsehood (al-zoor) even if no-one else is harmed by it, as in the aayah forbidding zihaar (a form of divorce in which the man says to his wife "You are to me like the back of my mother"), where He says (interpretation of the meaning): "… And verily, they utter an ill word and a lie (zooran)…" [al-Mujaadilah 58:2]. And Allaah says (interpretation of the meaning): "… So shun the abomination of idols, and shun lying speech (false statements, al-zoor)." [al-Hajj 22:30]. So the one who does al-zoor is condemned in this fashion.
In the Sunnah: Anas ibn Maalik (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) came (to Madeenah) and they had two days in which they would (relax and) play. He said, "What are these two days?" They said, "We used to play (on these two days) during the Jaahiliyyah." The Messenger of Allaah (peace and blessings of Allaah be upon him) said: "Allaah has given you something better instead of them: Yawm al-Duhaa (Eid al-Adha) and Yawm al-Fitr (Eid al-Fitr)." [Reported by Abu Dawood]
This indicates clearly that the Prophet (peace and blessings of Allaah be upon him) definitely forbade his ummah to celebrate the festivals of the kuffaar, and he strove to wipe them out by all possible means. The fact that the religion of the People of the Book is accepted does not mean that their festivals are approved of or should be preserved by the ummah, just as the rest of their kufr and sins are not approved of. Indeed, the Prophet (peace and blessings of Allaah be upon him) went to great lengths to command his ummah to be different from them in many issues that are mubaah (permitted) and in many ways of worship, lest that lead them to be like them in other matters too. This being different was to be a barrier in all aspects, because the more different you are from the people of Hell, the less likely you are to do the acts of the people of Hell.
The first of them is: The hadeeth "Every people has its festival, and this is our festival" implies exclusivity, that every people has its own festival, as Allaah says (interpretation of the meaning): "For every nation there is a direction to which they face (in their prayers)…" [al-Baqarah 2:148] and "… To each among you, We have prescribed a law and a clear way…" [al-Maa'idah 5:48] This implies that each nation has its own ways. The laam in li-kulli ("for every", "to each") implies exclusivity. So if the Jews have a festival and the Christians have a festival, it is just for them, and we should not have any part in it, just as we do not share their qiblah (direction of prayer) or their laws.
The second of them is: one of the conditions set out by 'Umar ibn al-Khattaab (may Allaah be pleased with him) and agreed upon by the Sahaabah and by all the Fuqaha' after them is: that those of the People of the Book who have agreed to live under Islamic rule (ahl al-dhimmah) should not celebrate their festivals openly in Daar al-Islam (lands under Islamic rule). If the Muslims have agreed to prevent them from celebrating openly, how could it be right for the Muslims to celebrate them? If a Muslim celebrates them, is that not worse than if a kaafir does so openly?
The only reason that we forbade them to celebrate their festivals openly is because of the corruption involved in them, because of the sin or symbols of sin. In either case, the Muslim is forbidden from sin or the symbols of sin. Even if there was no evil involved apart from the kaafir feeling encouraged to celebrate openly because of the Muslim's actions, how can a Muslim do that? The evil involved (in their festivals) will be explained below, in sha Allaah.
Al-Bayhaqi reported with a saheeh isnaad in Baab karaahiyat al-dukhool 'ala ahl al-dhimmah fi kanaa'isihim wa'l-tashabbuh bihim yawmi nawroozihim wa maharjaanihim (Chapter on the abhorrence of entering the churches of ahl al-dhimmah on the occasion of their New Year and other celebrations): From Sufyaan al-Thawri from Thawr ibn Yazeed from 'Ata' ibn Deenaar who said: 'Umar said: "Do not learn the language of the non-Arabs, do not enter upon the mushrikeen in their churches on their feast-days, for the wrath (of Allaah) is descending upon them."
'Umar ibn al-Khattaab said: "Avoid the enemies of Allaah on their festivals."
It was reported with a saheeh isnaad from Abu Usaamah: 'Awn told us from Abu'l-Mugheerah from 'Abd-Allaah ibn 'Amr: "Whoever lives in the land of the non-Arabs and celebrates their New Year and their festivals, and imitates them until he dies in that state, will be gathered with them on the Day of Resurrection."
'Umar forbade learning their languages, and even entering their churches on the day of their festival, so how about doing some of the things they do on those days, or doing things that are a part of their religion? Is not going along with their actions worse than learning their language? Is not doing some of the things they do on their festival worse than just entering upon them? If divine wrath is descending upon them on the day of their festival because of what they do, then is not the one who does what they do, or a part of it, also exposed to the same punishment? Do not the words "Avoid the enemies of Allaah on their festivals" mean that we should not meet them or join them on those days? So how about the one who actually celebrates their festivals?
'Abd-Allaah ibn 'Amr clearly stated: "Whoever lives in the land of the non-Arabs and celebrates their New Year and their festivals, and imitates them until he dies in that state, will be gathered with them on the Day of Resurrection."
This implies that the one who joins in with them in all of these matters is a kaafir, or that doing this is one of the major sins (kabaa'ir) that will doom one to Hell; the former meaning is what is apparent from the wording.
He mentioned – and Allaah knows best – the one who lives in their land, because at the time of 'Abd-Allaah ibn 'Amr and the other Sahaabah, they used to forbid open celebration of kaafir festivals in the Muslim lands, and none of the Muslims imitated them in their festivals; that was possible only when living in the lands of the kaafirs.
'Ali (may Allaah be pleased with him) refused to even acknowledge the name of their festivals which were exclusively theirs, so how about actually celebrating them?
Ahmad mentioned the meaning of the reports narrated from 'Umar and 'Ali (may Allaah be pleased with them) on this topic, and his companions discussed the matter of festivals.
Imaam Abu'l-Hasan al-Aamidi said: the one who is known as Ibn al-Baghdaadi said in his book 'Umdat al-Haadir wa Kifaayat al-Musaafir: "It is not permitted to attend the festivals of the Christians and Jews". Ahmad stated this in the report of Muhannaa, and his evidence for that is the aayah (interpretation of the meaning): 'And those who do not witness falsehood (al-zoor)…' [al-Furqaan 25:72] He said: "(This is) al-Sha'aaneen and their festivals. He said: The Muslims are to be prevented from entering upon them in their synagogues and churches."