a matter of ordinary custom, what then of imitating them in something far more serious?

The majority of imams disapproved of eating what they slaughter for their festivals and sacrificial offerings—whether regarding it as forbidden or merely discouraged—classifying it among that over which a name other than Allah’s has been invoked and that which is slaughtered on sacrificial altars. Likewise, Muslims were forbidden to assist them in their festivals through gifts or trade. They stated that it is not lawful for Muslims to sell Christians anything that serves their festival—not meat, blood, or clothing. Nor should they be lent a riding animal or assisted in any aspect of their religion, for this glorifies their polytheism and assists them in their disbelief. Rulers should forbid Muslims from doing this, because Allah Most High says:

“Cooperate in righteousness and piety, but do not cooperate in sin and aggression.”

Moreover, a Muslim is not permitted to help them drink wine by pressing grapes for it or by similar means. How, then, could he assist them in practices that are among the rites of disbelief? And if he is not permitted to assist them, what then if he performs those practices himself?

And Allah knows best. These are the words of Ahmad ibn Taymiyyah.