´It was narrated from Umm Salamah that:` the Messenger of Allah (ﷺ) swore to keep away from some of his wives for a month. On the twenty-ninth day, in the evening or the morning, it was said: "O Messenger of Allah, only twenty-nine days have passed." He said: "The month is twenty-nine days."
Hadith Referenceسنن ابن ماجه / كتاب الطلاق / 2061
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه