Question: It is written in the book Endless Bliss that he who deems something that is haram according to all the four madhahib to be halal or who deems something that is halal according to all the four madhahib to be haram becomes a disbeliever. Could you give some examples to illustrate the subject?
ANSWER
I will give some examples:

1. During the time when a woman is menstruating (hayd) or experiencing postnatal bleeding (nifas), it is haram (forbidden) in all the four madhahib (pl. of madhhab) for her to perform salat, to fast, or to enter a mosque. (Endless Bliss)

2. It is haram in all the four madhahib for a man to look at a non-mahram woman's body, with the exception of her face and inner and outer surfaces of her hands. (Radd-ul-mukhtar)

3. It is haram in all the four madhahib for a junub man or woman to perform, before he or she takes a ghusl, any act of worship that is not allowed to be performed without wudu. (Al-Fiqh 'Ala Al-Madhahib Al-Arba'ah)

[junub: a person who is in a state of impurity following sexual intercourse, wet dream, or seminal discharge]

4. The nikah called mut'a or a temporary nikah is haram and invalid according to all the four madhahib. (Mizan)

[The nikah of mut’a means to enter into a temporary cohabitation agreement with a woman without any witnesses by paying her a certain amount of money.]

5. It is written in Durr-ul-mukhtar: "It is permissible and beautiful to recite the Qur’an al-karim with taghanni provided that no letter is added and the words are not misspelled or mispronounced. Otherwise, it is haram. There is the fear of kufr [disbelief] if one says, ‘How nicely you recite!’ to someone who performs taghanni in a way that distorts the Qur’an al-karim." Ibn Abidin explaining this statement in his commentary, writes, “It was said that a person will become a disbeliever if he says, ‘How beautifully you recite!’ to a hafiz who recites with taghanni. This is because he who says ‘good’ for something that is haram according to all the four madhahib will become a disbeliever." (Radd-ul-mukhtar)

6. Intoxicating drinks, like wine, are najasat al-ghaliza (gross filth) in all the four madhahib. (Al-Fiqh 'Ala Al-Madhahib Al-Arba'ah)

7. Saying the takbir (Allahu akbar) at the beginning of salat is fard in all the four madhahib. (İslam Ahlakı)

8. It is not permissible for a man to wear a gold ring in all the four madhahib. (Mawahib-i ladunniya)

9. Anyone who disbelieves the ijma' (unity of the mujtahids of the same era on the rules of the same thing) of the four madhahib becomes a disbeliever. (Radd-ul-mukhtar)

10. It is fard in all the four madhahib to inform Muslims about the harm of a bid'a that has become widespread. In fact, there is ijma-i Ummat on this fact. (Maktubat-i Ma'thumiyya)

[ijma-i Ummat: the agreement of As-hab-i kiram and Tabi'in on a matter]

A person who does or says something that is haram to do or say according to all the four madhahib by liking, approving, or deeming it to be halal becomes a disbeliever. He who does so will not become a disbeliever, however, if he has to do it as a result of oppression or following customs and his nafs or ineluctabilities involved in making a life, unwillingly and regretfully.