The Prophet ﷺ intended to practice Iʿtikaf and when he reached the place where he intended to perform Iʿtikaf, he saw some tents, the tents of ʿAisha, Hafsa and Zainab. So, he said, "Do you consider that they intended to do righteousness by doing this?" And then he went away and did not perform Iʿtikaf (in Ramadan) but performed it in the month of Shawwal for ten days.  

أَنَّ النَّبِيَّ ﷺ أَرَادَ أَنْ يَعْتَكِفَ فَلَمَّا انْصَرَفَ إِلَى الْمَكَانِ الَّذِي أَرَادَ أَنْ يَعْتَكِفَ إِذَا أَخْبِيَةٌ خِبَاءُ عَائِشَةَ وَخِبَاءُ حَفْصَةَ وَخِبَاءُ زَيْنَبَ فَقَالَ آلْبِرَّ تَقُولُونَ بِهِنَّ ثُمَّ انْصَرَفَ فَلَمْ يَعْتَكِفْ حَتَّى اعْتَكَفَ عَشْرًا مِنْ شَوَّالٍ