Sahih al-Bukhari 5289
Narrated Anas bin Malik:
Allah's Messenger (ﷺ) took an oath that he would abstain from his wives, and at that time his leg had been 
sprained (dislocated). So he stayed in the Mashruba (an attic room) of his for 29 days. Then he came 
down, and they (the people) said, "O Allah's Messenger (ﷺ)! You took an oath to abstain from your wives for 
one month." He said, "The month is of twenty nine days."
حَدَّثَنَا إِسْمَاعِيلُ بْنُ أَبِي أُوَيْسٍ، عَنْ أَخِيهِ، عَنْ سُلَيْمَانَ، عَنْ حُمَيْدٍ الطَّوِيلِ، أَنَّهُ سَمِعَ أَنَسَ بْنَ مَالِكٍ، يَقُولُ آلَى رَسُولُ اللَّهِ صلى الله عليه وسلم مِنْ نِسَائِهِ، وَكَانَتِ انْفَكَّتْ رِجْلُهُ فَأَقَامَ فِي مَشْرُبَةٍ لَهُ تِسْعًا وَعِشْرِينَ، ثُمَّ نَزَلَ فَقَالُوا يَا رَسُولَ اللَّهِ آلَيْتَ شَهْرًا‏.‏ فَقَالَ ‏
"‏ الشَّهْرُ تِسْعٌ وَعِشْرُونَ ‏"‏‏.‏