TIRMIDHI 791:
from ʿĀʾishah —
"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."
الترمذي ٧٩١:
عن عاءشه —
كَانَ رَسُولُ اللَّهِ ﷺ إِذَا أَرَادَ أَنْ يَعْتَكِفَ صَلَّى الْفَجْرَ ثُمَّ دَخَلَ فِي مُعْتَكَفِهِ