Muhammad bin 'Aabad bin Ja'far محمد بن عباد بن جعفر بن رفاعة · The Chapters on Divorce

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."