بسم الله الحرمن الرحيم
If the items are specifically connected to their false and baseless beliefs and practices then it would not be permissible for trade. i.e. the items are a symbol of their falsehood and are not used for any other purpose except for their worship and rituals. Examples of these items are crucification crosses, statues, idols, Christmas symbols, cards etc.
This rule also applies to items which are generally used, except that the symbols of shirk and kufr are displayed on them (i.e printed, painted, engraved, embroidered or attached in any way). If however, it is possible to remove or disfigure those symbols from the items, only then it would be permissible to sell it.
Imam al-Bukhari narrates on the authority of Aa’isha may Allaah be pleased with her that:
أن النبي صلى الله عليه وسلم لم يكن يترك في بيته شيئا فيه تصاليب إلا نقضه
“The Holy Prophet ﷺ would not leave anything in his house on which there was a cross but he would alter it.”
The reason from this prohibition has nothing to do with the item itself in terms of its contents and ingredients. It is because, by trading in such items, one is directly assisting and promoting evil and shirk, which is forbidden as it goes against the spirit of Tawheed. Allah ﷻ mentions in the Holy Quran:
وتعاونوا على البر والتقوى ولا تعاونوا على الإثم والعدوان واتقوا الله إن الله شديد العقاب
And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allah, indeed, Allah is severe in penalty.
If however, the items can be used for multiple purposes, it would be permissible to trade it (i.e. it is used for their rituals as well as other things which are permissible).
And Allah Ta’āla Knows Best
Mufti Kaleem Muhammad
Darul Iftaa, Jaamia Madinatul Uloom (Trinidad)