What is the ruling on selling food to a Muslim if it is known that he will use it to celebrate Christmas?

The fatwa adopted by us is that celebrating birthdays is forbidden and impermissible. They based their ruling on what Ibn ‘Uthaymeen said: that Islam has no festivals for any occasion other than the two Eids of Fitr and Adha, and Friday. If we rule that celebrating it is forbidden, then it is not permissible to sell food or other items to those who will use them for such celebrations, because that falls under cooperating in sin and aggression.

Some scholars, such as Dr. Salman Al-Ouda, hold the view that personal birthday celebrations are permissible, and selling their related supplies is also permissible, because they do not have a doctrinal dimension and only concern the individual, unlike things with a religious character.