Is it permissible for a Dhimmi (non-Muslim under Muslim protection) to perform 'Ila' (oath of abstinence)?
General Chapter
Al-Mughni
Book of the Oath of Abstention (Ila')
Primary text
The Ila sworn by a Dhimmi is valid, and the obligations applicable to Muslims apply to them if they make demands upon us. This is the position held by Abu Hanifa, Al-Shafi'i, and Abu Thawr. If the Dhimmi embraces Islam, the ruling pertaining to their Ila does not cease. The evidence is the saying of Allah the Exalted: 'For those who swear to abstain from their wives, there is a waiting period of four months' (Quran 2:226). Furthermore, since they restrict themselves from intercourse through an oath, they are considered Mu'li, just like a Muslim.
Supporting text
If the oath was specifically in the name of Allah, Imam Malik holds that the ruling of Ila is nullified if the person embraces Islam. Abu Yusuf and Muhammad state that if the oath was by Allah, the person is not considered Mu'li because he would not be considered breaking his oath if he had intercourse, given that he was not obligated (to fulfill it prior to Islam). However, if the oath involved divorce or manumission, then he is considered Mu'li because the manumission and divorce pronounced by him are valid.