"One morning, we saw the wives of the Prophet weeping, and each one of them had her family with her. I entered the Masjid and found it filled with people. Then 'Umar, may Allah be pleased with him, came, and went to the Prophet who was in his room. He greeted him with the Salam but no one answered. He greeted him again but no one answered. He greeted him (a third time) but no one answered. So he went back and called out: 'Bilal!' He came to the Prophet and said: 'Have you divorced your wives?' He said: 'No, but I have sworn an oath of abstention from them for a month.' So he stayed away from them for twenty-nine days, then he came and went into his wives." (Using translation from Nasāʾī 3455)  

أَصْبَحْنَا يَوْمًا وَنِسَاءُ النَّبِيِّ ﷺ يَبْكِينَ عِنْدَ كُلِّ امْرَأَةٍ مِنْهُنَّ أَهْلُهَا فَدَخَلْتُ الْمَسْجِدَ فَإِذَا هُوَ مُلِأَ مِنَ النَّاسِ قَالَ فَجَاءَ عُمَرُ فَصَعِدَ إِلَى النَّبِيِّ ﷺ وَهُوَ فِي عُلِّيَّةٍ لَهُ فَسَلَّمَ عَلَيْهِ فَلَمْ يُجِبْهُ أَحَدٌ ثُمَّ سَلَّمَ فَلَمْ يُجِبْهُ أَحَدٌ فَرَجَعَ فَنَادَى بِلَالًا فَدَخَلَ عَلَى النَّبِيِّ ﷺ فَقَالَ أَطَلَّقْتَ نِسَاءَكَ؟ قَالَ «لَا وَلَكِنِّي آلَيْتُ مِنْهُنَّ شَهْرًا» فَمَكَثَ تِسْعًا وَعِشْرِينَ ثُمَّ نَزَلَ فَدَخَلَ عَلَى عَائِشَةَ  

"The Prophet swore an oath of abstention from his wives for a month and stayed in his room for twenty-nine days. It was said: 'O Messenger of Allah, did you not swear an oath of abstention for a month?' He said: 'This month is twenty-nine days.'" (Using translation from Nasāʾī 3456)  

آلَى النَّبِيُّ ﷺ مِنْ نِسَائِهِ شَهْرًا فَقَعَدَ فِي مَشْرُبَةٍ لَهُ فَمَكَثَ تِسْعًا وَعِشْرِينَ لَيْلَةً ثُمَّ نَزَلَ فَقِيلَ يَا رَسُولَ اللهِ أَلَسْتَ آلَيْتَ عَلَى شَهْرٍ؟ قَالَ «الشَّهْرُ تِسْعٌ وَعِشْرُونَ»