Prohibition of Observing an Optional Saum (Fast) by a Woman without the Permission of her Husband

Abu Hurairah (May Allah be pleased with him) said:
The Prophet ﷺ said, "Does he who raises up his head before the Imam not fear that Allah will make his head that of a donkey or make his appearance similar to that of donkey?"

[Al-Bukhari and Muslim].

عن أبي هريرة رضي الله عنه أن النبي ﷺ قال: "أما يخشى أحدكم إذا رفع رأسه قبل الإمام أن يجعل الله رأسه رأس حمار! أو يجعل الله صورته صورة حمار" ((متفق عليه)).