"I wanted to enter the House and pray therein, so the Messenger of Allah took me by the hand and took me into the Hijr and said: 'If you want to enter the House, then pray here, for it is part of the House, but your people made it too small when they built it.'" (Sahih) Chatper 130. Reciting The Takbir In the Corners Of the Kabah (Using translation from Nasāʾī 2912)  

أَنْ أَدْخُلَ الْبَيْتَ فَأُصَلِّيَ فِيهِ فَأَخَذَ رَسُولُ اللهِ ﷺ بِيَدِي فَأَدْخَلَنِي الْحِجْرَ فَقَالَ «إِذَا أَرَدْتِ دُخُولَ الْبَيْتِ فَصَلِّي هَاهُنَا فَإِنَّمَا هُوَ قِطْعَةٌ مِنَ الْبَيْتِ وَلَكِنَّ قَوْمَكِ اقْتَصَرُوا حَيْثُ بَنَوْهُ»