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."
أَنَّ رَسُولَ اللَّهِ ﷺ آلَى مِنْ بَعْضِ نِسَائِهِ شَهْرًا فَلَمَّا كَانَ تِسْعَةً وَعِشْرِينَ رَاحَ أَوْ غَدَا فَقِيلَ يَا رَسُولَ اللَّهِ إِنَّمَا مَضَى تِسْعٌ وَعِشْرُونَ فَقَالَ الشَّهْرُ تِسْعٌ وَعِشْرُونَ