Imām Ibn al-Qayyim Raḥimahullāh said:

✒ *Congratulating Kuffār Their Festivals Would Neither Earn You Their Respect Nor Their Pleasure So Beware Of Losing Your Religion!!*

قال الإمام ابن القيم رحمه الله : وأما التهنئة بشعائر الكفر المختصة به فحرام بالاتفاق ، مثل أن يهنئهم بأعيادهم وصومهم ، فيقول : عيد مبارك عليك ، أو تهنأ بهذا العيد ونحوه ، فهذا إن سلم قائله من الكفر فهو من المحرمات ، وهو بمنزلة أن يهنئه بسجوده للصليب ، بل ذلك أعظم إثماً عند الله ، وأشد مقتاً من التهنئة بشرب الخمر وقتل النفس وارتكاب الفرج الحرام ونحوه . وكثير ممن لا قدر للدين عنده يقع في ذلك ، ولا يدري قبح ما فعل فمن هنأ عبداً بمعصية أو بدعة أو كفر فقد تعرض لمقت الله وسخطه

Imām Ibn al-Qayyim Raḥimahullāh said: “And as for congratulating Kuffār on the rituals which are SPECIFIC to them, then it is ḤARĀM (FORBIDDEN) by the AGREEMENT (of Fuqahā), for example congratulating them on their festivals and fasts by saying: ‘A happy festival to you’ or ‘May you enjoy your festival,’ and so on, so if the one who says this has been saved from Kufr, it is STILL FORBIDDEN, and it is like congratulating someone for PROSTRATING to the CROSS, rather that (congratulating Kuffār) is GREATER of a SIN with Allāh.

And it is MORE HATEFUL (to Allāh) than congratulating someone for DRINKING WINE, or MURDERING an INNOCENT SOUL, or COMMITTING ADULTERY, and the likes of it, and many of those who have NO RESPECT for their religion fall into that (error); without REALISING the OFFENSIVENESS of their action, so whoever congratulates a person for his DISOBEDIENCE or BID’AH or KUFR thus exposes himself to the WRATH and ANGER of Allāh.”

● [أحكام أهل الذمة ١/١٦١]

As for those who say ‘Well we congratulate disbelievers Christmas and New Year out of courtesy and good manners’, then we say: O Miskeen the Messenger of Allāh Ṣallallāhu-‘Alaihi Wa Sallam and his Companions (Raḍi-Allāhu ‘Anhum) were more courteous and well-mannered than you and I yet they never congratulated Kuffār for their ‘Eīds or New Year,

And last but not least remember this 👇

ولن ترضى عنك اليهود ولا النصارى حتى تتبع ملتهم قل إن هدى الله هو الهدى ولئن اتبعت أهواءهم بعد الذي جاءك من العلم ما لك من الله من ولي ولا نصير

“Never will the Jews nor the Christians be PLEASED with you TILL you FOLLOW their RELIGION. Say: 'Verily, the Guidance of Allāh (i.e. Islamic Monotheism) that is the (only) Guidance. And if you (O Muḥammad, Peace be upon him) were to follow their (Jews and Christians) desires after what you have received of Knowledge (i.e. the Qur’ān), then you would have against Allāh neither any Walī (protector or guardian) nor any helper.” — [al-Qur’ān 2:120]