It is written in Birgiwi Wasiyyetnamesi Sharhi, “The second type of things which disbelievers use are the things which are symptoms of disbelief, symptoms of denying and disbelieving the shari’at  and Islam, and it is wajib  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 (disbelief) to wear (or use) things specially worn or used by priests during their worships. This is called Kufr-i hukmi.” It is written in the basic books of fiqh  by Islamic ’alims  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 din will not be saved from Hell. Today, Allahu ta’ala has made His din known everywhere in the world, and He has made learning iman (belief), the fards , the harams (prohibitions) and the halals (permitted), 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.
 makruh: (act, thing) improper, disliked and abstained by the Prophet (‘alaihi ‘s-salam); makruh tahrima: prohibited with much stress.
 mubah: (act, thing) neither ordered nor prohibited; permitted.
 bid’at: (pl. bida’) heresy; false, disliked belief or practice that did not exist in the four sources of Islam but which has been introduced later as an Islamic belief or ‘ibada in expectation of thawab (blessings) ; heresy.
 Shari’at: (pl. of Shari’a) i) rules and commandments as a whole of the religion. ii) religion.
 wajib: (act, thing) never omitted by the Prophet, so almost as compulsory as fard and not to be omitted. Wajib al-wujud: Being whose existence is indispensable and nonexistence is impossible.
 fiqh: knowledge dealing with what Muslims should do and should not do; actions, a’mal, ‘ibadat.
 ‘alim: i) scholar trained in Islamic knowledge and his contemporary science. ii) (pl. ‘ulama’) Muslim scholar.
 fard: an act or thing that is commanded by Allahu ta’ala in the Qur’an al-kerim. Fard (or fard) means (any behaviour or thought or belief which is) obligatory. Islam’s open commandments are called fard (pl. faraid).