"The Messenger of Allah swore not to come to his wives for a month, and twenty-nine days passed. I said: 'Did you not wives to keep away from you wives for a month? I have counted twenty-nine days.' The Messenger of Allah said: 'The month is twenty-nine days."' (Using translation from Nasāʾī 2131)
أَنَّهَا قَالَتْ أَقْسَمَ رَسُولُ اللهِ ﷺ أَنْ لَا يَدْخُلَ عَلَى نِسَائِهِ شَهْرًا قَالَتْ فَلَبِثَ تِسْعًا وَعِشْرِينَ قَالَتْ فَكُنْتُ أَوَّلَ مَنْ بَدَأَ بِهِ فَقُلْتُ لِلنَّبِيِّ ﷺ أَلَيْسَ كُنْتَ أَقْسَمْتَ شَهْرًا فَعَدَدْتُ الْأَيَّامَ تِسْعًا وَعِشْرِينَ؟ فَقَالَ النَّبِيُّ ﷺ الشَّهْرُ تِسْعٌ وَعِشْرُونَ