(96) باب الصَّلاَةِ بَيْنَ السَّوَارِي فِي غَيْرِ جَمَاعَةٍ
Narrated Ibn `Umar:
The Prophet (ﷺ) entered the Ka`ba along with Usama bin Zaid, `Uthman bin Talha and Bilal and remained there for a long time. When they came out, I was the first man to enter the Ka`ba. I asked Bilal "Where did the Prophet (ﷺ) pray?" Bilal replied, "Between the two front Pillars."
Reference: Sahih al-Bukhari 504
In-book reference: Book 8, Hadith 151
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 9, Hadith 483