All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is impermissible to sell whatever the disbelievers use in their false religious rituals, such as incense or other items that they offer to their false gods or use during their prayers, because this constitutes helping them in committing sins. As for selling them lawful food and beverages that they consume in their religious festivals and that are not used in their false religious rituals, the preponderant opinion is that it is disliked.
Al-Fataawa Al-Fiqhiyyah Al-Kubra authored by Ibn Hajar Al-Makki reads: “(He was asked) what is the ruling on selling things like musk to a disbeliever if the (Muslim) seller knows that he buys it to apply it to his idol, and selling an animal to a belligerent disbeliever if the seller knows that he will kill it, rather than slaughter it, and eat its meat? (He replied): The sale is forbidden in both cases, as implied by the scholars’ statement that it is impermissible for a seller to sell any item which he knows will be used in committing an act of disobedience. Applying perfume to a worshipped idol and consuming a killed, not slaughtered, animal are grave sins, even for them, because the preponderant opinion is that the disbelievers are required to observe the applied teachings of Islam (Sharee‘ah obligations and prohibitions) just like Muslims. Accordingly, it is impermissible to help them commit any violation of the Sharee‘ah by selling them what is used for such purposes. In this case, knowing that the buyer will use the purchased items in what is forbidden is the same as believing that he will most likely do so as far as the religious ruling in this regard is concerned, and Allah knows best.” [End of quote]
Haashiyat Ad-Dusooqi reads: “It is disliked for us to sell food or other items like clothing, renting out riding animals, ships, and the like to a disbeliever to use them for his religious festival.” [End of quote]
Shaykhul-Islam Ibn Taymiyyah said: “If what they are buying is used in the very prohibited act, such as a cross, palm branches, a baptismal font, incense, offering animal sacrifices to other than Allah, or an image, and the like, there is no doubt that it is forbidden to sell to them such items. The same applies to selling to them (grape) juice to make wine and building a church for them. As for the food, beverages, and clothing they use in their religious festivals, the fundamental principles of Imam Ahmad’s School of Fiqh and others indicate that it is disliked.” [End of quote, Iqtidhaa’ As-Siraat Al-Mustaqeem Li-Mukhaalafat Ashaab Al-Jaheem]
It is better for a Muslim to refrain from entering in a business partnership with non-Muslims. Al-Buhooti said in Khashshaaf Al-Qinaa': “It is disliked for a Muslim to enter in a partnership with a Magi, a pagan, and similar disbelievers who worship other than Allah, The Exalted. The preponderant opinion in this regard is that it is impermissible even if the Muslim is the one given free-hand to act and conduct the business. Imam Ahmad said with regard to a business partnership with a Magi, ‘I do not like that he (the Muslim) should intermix and engage in business transactions with him because he deems lawful what the Muslim deems unlawful.’” [End of quote]
Allah Knows best.