Some one came to Ibn Umar in his house and said: The Messenger of Allah (ﷺ) has entered the Kabah." So Ibn Umar said, I (Ibn Umar) came and found that the Messenger of Allah (ﷺ) had come out, and I found Bilal standing at the door. I said: "O Bilal, did the Messenger of Allah (ﷺ) pray inside the Kabah?' He said: "Ues." I said: "Where>" He said: "Between these two columns, two Rakahs. Then he came out and prayed two Rakahs in front of the Kabah."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ حَدَّثَنَا سَيْفُ بْنُ سُلَيْمَانَ، قَالَ سَمِعْتُ مُجَاهِدًا، يَقُولُ أُتِيَ ابْنُ عُمَرَ فِي مَنْزِلِهِ فَقِيلَ هَذَا رَسُولُ اللَّهِ صلى الله عليه وسلم قَدْ دَخَلَ الْكَعْبَةَ فَأَقْبَلْتُ فَأَجِدُ رَسُولَ اللَّهِ صلى الله عليه وسلم قَدْ خَرَجَ وَأَجِدُ بِلاَلاً عَلَى الْبَابِ قَائِمًا فَقُلْتُ يَا بِلاَلُ أَصَلَّى رَسُولُ اللَّهِ صلى الله عليه وسلم فِي الْكَعْبَةِ قَالَ نَعَمْ . قُلْتُ أَيْنَ قَالَ مَا بَيْنَ هَاتَيْنِ الأُسْطُوَانَتَيْنِ رَكْعَتَيْنِ ثُمَّ خَرَجَ فَصَلَّى رَكْعَتَيْنِ فِي وَجْهِ الْكَعْبَةِ .
sunnah.com