"The Prophet would perform I'tikaf during the last ten (days) of Ramadan until Allah took him."  

أَنَّ النَّبِيَّ ﷺ كَانَ يَعْتَكِفُ الْعَشْرَ الأَوَاخِرَ مِنْ رَمَضَانَ حَتَّى قَبَضَهُ اللَّهُ قَالَ وَفِي الْبَابِ عَنْ أُبَىِّ بْنِ كَعْبٍ وَأَبِي لَيْلَى وَأَبِي سَعِيدٍ وَأَنَسٍ وَابْنِ عُمَرَ  

"When the Messenger of Allah wanted to perform I'tikaf, he would perform Fajr prayer and then he would enter his place of I'tikaf."  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا أَرَادَ أَنْ يَعْتَكِفَ صَلَّى الْفَجْرَ ثُمَّ دَخَلَ فِي مُعْتَكَفِهِ