"Messenger of Allah ﷺ, Usama bin Zaid, Bilal, and ʿUthman bin abu Talha entered the Kaʿba and then closed its door. When they opened the door I was the first person to enter (the Kaʿba). I met Bilal and asked him, "Did Messenger of Allah ﷺ offer a prayer inside (the Kaʿba)?" Bilal replied in the affirmative and said, "(The Prophet ﷺ offered the prayer) in between the two right pillars." (Using translation from Bukhārī 1598)  

دَخَلَ رَسُولُ اللهِ ﷺ الْبَيْتَ هُوَ وَأُسَامَةُ بْنُ زَيْدٍ وَبِلَالٌ وَعُثْمَانُ بْنُ طَلْحَةَ فَأَغْلَقُوا عَلَيْهِمْ فَلَمَّا فَتَحُوا كُنْتُ أَوَّلَ مَنْ وَلَجَ فَلَقِيتُ بِلَالًا فَسَأَلْتُهُ هَلْ صَلَّى فِيهِ رَسُولُ اللهِ ﷺ؟ قَالَ «نَعَمْ صَلَّى بَيْنَ الْعَمُودَيْنِ الْيَمَانِيَّيْنِ»