Is it permissible for someone who has vowed to Allah to abandon masturbation to engage in it if he fears falling into fornication, or does his vow prevent him from doing so?

Masturbation is forbidden by the majority of scholars, but necessity or severe hardship may permit a lesser evil. Hence, a group of scholars has stipulated the permissibility of masturbation if there is a real fear of falling into zina (unlawful sexual intercourse). This is the view of Ahmad and others, and it is a way of repelling the greater of two evils with the lesser.

This state of necessity is governed by two conditions: 1. The fear of zina must be real and highly probable, for instance, if a person is in a place where zina is easily accessible and their sexual desire becomes so intense that they cannot control themselves. 2. They must be unable to remove this necessity through permissible means, such as abstaining from the causes of zina or getting married if they are capable of it.

If a Muslim makes a covenant with Allah to abandon masturbation, then this covenant is subject to the ruling of an oath. If they are compelled to masturbate out of fear of zina after losing control of themselves, and they see no other option but one of the two, then masturbation in this case is the lesser of two harms, and they must offer expiation for breaking an oath (kaffarat yamin (definition)).