Messenger of Allah ﷺ mentioned that he would practice Iʿtikaf in the last ten days of Ramadan. ʿAisha asked his permission to perform Iʿtikaf and he permitted her. Hafsa asked ʿAisha to take his permission for her, and she did so. When Zainab bint Jahsh saw that, she ordered a tent to be pitched for her and it was pitched for her. Messenger of Allah ﷺ used to proceed to his tent after the prayer. So, he saw the tents ans asked, "What is this?" He was told that those were the tents of Aisha, Hafsa, and Zainab. Allah's Apostle said, "Is it righteousness which they intended by doing so? I am not going to perform Iʿtikaf." So he returned home. When the fasting month was over, he performed Itikar for ten days in the month of Shawwal. (Using translation from Bukhārī 2045)  

أَنَّ رَسُولَ اللهِ ﷺ «يَعْتَكِفُ الْعَشْرَ الْأَوَاخِرَ مِنْ شَهْرِ رَمَضَانَ» فَاسْتَأْذَنَتْهُ عَائِشَةُ فَأَذِنَ لَهَا فَسَأَلَتْ حَفْصَةُ عَائِشَةَ أَنْ تَسْتَأْذِنَ لَهَا فَفَعَلَتْ فَلَمَّا رَأَتْ زَيْنَبُ بِنْتُ جَحْشٍ أَمَرَتْ بِبِنَائِهَا فَبُنِيَ وَكَانَ رَسُولُ اللهِ ﷺ إِذَا صَلَّى انْصَرَفَ إِلَى بِنَائِهِ فَبَصُرَ بِالْأَبْنِيَةِ فَقَالَ «مَا هَذَا؟» فَقَالُوا هَذَا بِنَاءُ عَائِشَةَ وَحَفْصَةَ وَزَيْنَبَ فَقَالَ «آلْبِرَّ يُرِدْنَ بِهَذَا؟ مَا أَنَا بِمُعْتَكِفٍ» فَرَجَعَ فَلَمَّا أَفْطَرَ اعْتَكَفَ عَشْرًا مِنْ شَوَّالٍ