The Prophet ﷺ entered the Kaʿba along with Usama bin Zaid, ʿUthman bin Talha and Bilal and remained there for a long time. When they came out, I was the first man to enter the Kaʿba. I asked Bilal "Where did the Prophet ﷺ pray?" Bilal replied, "Between the two front Pillars."  

دَخَلَ النَّبِيُّ ﷺ الْبَيْتَ وَأُسَامَةُ بْنُ زَيْدٍ وَعُثْمَانُ بْنُ طَلْحَةَ وَبِلاَلٌ فَأَطَالَ ثُمَّ خَرَجَ وَكُنْتُ أَوَّلَ النَّاسِ دَخَلَ عَلَى أَثَرِهِ فَسَأَلْتُ بِلاَلاً أَيْنَ صَلَّى قَالَ بَيْنَ الْعَمُودَيْنِ الْمُقَدَّمَيْنِ  

ʿAbdullah bin ʿUmar said, "Messenger of Allah ﷺ entered the Kaʿba along with Usama bin Zaid, Bilal and ʿUthman bin Talha Al-Hajabi and closed the door and stayed there for some time. I asked Bilal when he came out, 'What did the Prophet ﷺ do?' He replied, 'He offered prayer with one pillar to his left and one to his right and three behind.' In those days the Kaʿba was supported by six pillars." Malik said: "There were two pillars on his (the Prophet's) right side."  

أَنَّ رَسُولَ اللَّهِ ﷺ دَخَلَ الْكَعْبَةَ وَأُسَامَةُ بْنُ زَيْدٍ وَبِلاَلٌ وَعُثْمَانُ بْنُ طَلْحَةَ الْحَجَبِيُّ فَأَغْلَقَهَا عَلَيْهِ وَمَكَثَ فِيهَا فَسَأَلْتُ بِلاَلاً حِينَ خَرَجَ مَا صَنَعَ النَّبِيُّ ﷺ قَالَ جَعَلَ عَمُودًا عَنْ يَسَارِهِ وَعَمُودًا عَنْ يَمِينِهِ وَثَلاَثَةَ أَعْمِدَةٍ وَرَاءَهُ وَكَانَ الْبَيْتُ يَوْمَئِذٍ عَلَى سِتَّةِ أَعْمِدَةٍ ثُمَّ صَلَّى وَقَالَ لَنَا إِسْمَاعِيلُ حَدَّثَنِي مَالِكٌ وَقَالَ عَمُودَيْنِ عَنْ يَمِينِهِ