بُلُوغُ الْمَرَامِ
Bulugh al-Maram 700
Fasting
وَعَنْهَا قَالَتْ: { كَانَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -إِذَا أَرَادَ أَنْ يَعْتَكِفَ صَلَّى اَلْفَجْرَ, ثُمَّ دَخَلَ مُعْتَكَفَهُ } مُتَّفَقٌ عَلَيْهِ [1] .
’A’isha (RAA) narrated, "Whenever the Messenger of Allah (ﷺ) intended to make I'tikaf he would pray the morning prayer and then he would enter the place of his I’tikaf (i.e. the place, which he had prepared for his I'tikaf inside the mosque)." Agreed upon.
Arabic/English book reference: Book 5, Hadith 720