Ibni ‘Abidîn ‘rahmatullâhi aleyh’ in discussing the makrûhs of namâz says: “Things which disbelievers do and use are of two types: The first ones are things which they do as customs, that is, things which each nation, each country does as its customs. Out of these, doing or using things that are not harâm and that are useful is never a sin. [Wearing trousers, fez, different types of shoes, using spoons and forks, eating meals at a table, putting each person’s meal in a dish in front of him, cutting the bread in slices with a knife, and using various tools and gadgets are all behaviours concerning customs and are mubâh. It is not a bid’at or a sin to use them.] Rasûlullah put on shoes especially made for priests.”
It is written in Birgiwî Wasiyyetnâmesi Serhi, “The second type of things which disbelievers use are the things which are symptoms of disbelief, symptoms of denying and disbelieving the sharî’at and Islam, and it is wâjib for us to debase them. One who does or uses them becomes a disbeliever. They cannot be used unless one is threatened with death or with the cutting off of one’s limbs or some other reasons causing these results such as severe thrashing or imprisonment or the taking away of all one’s property. Also, he who does or uses one of them, which is commonly known, without knowing or as a joke in order to make people laugh, becomes a disbeliever. For example, it is kufr to wear (or use) things specially worn or used by priests during their worships. This is called Kufr-i hukmî.” It is written in the basic books of fiqh by Islamic ‘âlims that to wear the things which are peculiar means in the worships of the disbelievers, infidels, is kufr.
He who is deceived because he does not know his dîn will not be saved from Hell. Today, Allahu ta’âlâ has made His dîn known everywhere in the world, and He has made learning îmân, the fards, the harâms and the halâls, beautiful morals very easy. Everybody should learn as much as necessary and this is a fard. One who does not learn them is deemed to have disobeyed the fard. But a person who says there is no need to learn them or who gives no importance to them becomes a disbeliever.