Abu Hurairah (May Allah be pleased with him) said:
The Messenger of Allah (ﷺ) said, "It is not lawful for a woman to observe an optional Saum (fast) without the permission of her husband when he is at home. Nor should she allow anyone to enter his house without his permission."[Al-Bukhari and Muslim].
App reference: Book 18, Hadith 240
Arabic/English book reference: Book 18, Hadith 1750