All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Allaah, The Exalted, has underlined in His Book that there is no harm in a Muslim treating non-combatant disbelievers kindly. Allaah, The Exalted, says (what means): {Allaah does not forbid you from those who do not fight you because of religion and do not expel you from your homes - from being righteous toward them and acting justly toward them. Indeed, Allaah loves those who act justly.* Allaah only forbids you from those who fight you because of religion and expel you from your homes and aid in your expulsion - [forbids] that you make allies of them. And whoever makes allies of them, then it is those who are the wrongdoers.}[Quran 60:8-9] Fatwa 7885 highlights the permissibility of interacting with non-Muslims, treating them kindly and helping them solve their problems. This, however, does not include helping them commit a prohibited act such as assisting them in celebrating their religious occasions and festivals that are considered religious rituals by means of lending them money or the like.
Also, it is impermissible for a Muslim to offer a loan to a disbeliever if he knows that he will spend it on something prohibited in Islam even if the disbeliever would repay the debt.
It has been highlighted in Fataawa 196791 and 131758 that it is impermissible for a Muslim to attend the religious celebrations and festivals of non-Muslims. Fataawa 12267 and 45347 underlines that it is permissible for a Muslim to accept the gifts and eat the food of non-Muslims – as long as they are lawful – even if the food is made during their religious celebrations.
For further information, please refer to Fatwa 88293 about the relationship between the Muslim and non-Muslim (and its due boundaries in Islam).
Allaah Knows best.