Where did Allah's Apostle ﷺ observe prayer? They said: At this very place. I, however, forgot to ask them about the (number of) rak'ahs that he observed.  

أَنَّهُ انْتَهَى إِلَى الْكَعْبَةِ وَقَدْ دَخَلَهَا النَّبِيُّ ﷺ وَبِلاَلٌ وَأُسَامَةُ وَأَجَافَ عَلَيْهِمْ عُثْمَانُ بْنُ طَلْحَةَ الْبَابَ قَالَ فَمَكَثُوا فِيهِ مَلِيًّا ثُمَّ فُتِحَ الْبَابُ فَخَرَجَ النَّبِيُّ ﷺ وَرَقِيتُ الدَّرَجَةَ فَدَخَلْتُ الْبَيْتَ فَقُلْتُ أَيْنَ صَلَّى النَّبِيُّ ﷺ قَالُوا هَا هُنَا قَالَ وَنَسِيتُ أَنْ أَسْأَلَهُمْ كَمْ صَلَّى  

he came to the Kabah when the Prophet, Bilal and Usamah bin Zaid had enter it, and Uthman bin Talhah had shut the door. They stayed there for a while, then he opened the door and the Prophet came out. I (Ibn Umar) Climed the steps and entered the House and said: "Where did the Prophet pray?" They said: "Here." And I forgot to ask them how many (Rakahs) the Prophet had prayed inside the House.  

أَنَّهُ انْتَهَى إِلَى الْكَعْبَةِ وَقَدْ دَخَلَهَا النَّبِيُّ ﷺ وَبِلاَلٌ وَأُسَامَةُ بْنُ زَيْدٍ وَأَجَافَ عَلَيْهِمْ عُثْمَانُ بْنُ طَلْحَةَ الْبَابَ فَمَكَثُوا فِيهَا مَلِيًّا ثُمَّ فَتَحَ الْبَابَ فَخَرَجَ النَّبِيُّ ﷺ وَرَكِبْتُ الدَّرَجَةَ وَدَخَلْتُ الْبَيْتَ فَقُلْتُ أَيْنَ صَلَّى النَّبِيُّ ﷺ قَالُوا هَا هُنَا وَنَسِيتُ أَنْ أَسْأَلَهُمْ كَمْ صَلَّى النَّبِيُّ ﷺ فِي الْبَيْتِ  

[Machine] The Messenger of Allah ﷺ entered the house along with Bilal, Usama ibn Zaid, and Uthman ibn Talha. They knocked on the door and stayed for an hour, then he came out. When the door was opened, I was the first one to enter, so I asked Bilal, "Where did the Messenger of Allah ﷺ pray?" He said, "Between the two front pillars." I forgot to ask him how many raka'at he prayed.  

دَخَلَ رَسُولُ اللهِ ﷺ الْبَيْتَ هُو وَبِلَالٌ وَأُسَامَةُ بْنُ زَيْدٍ وَعُثْمَانُ بْنُ طَلْحَةَ فَأَجَافُوا الْبَابَ وَمَكَثُوا سَاعَةً ثُمَّ خَرَجَ فَلَمَّا فُتِحَ كُنْتُ أَوَّلَ مَنْ دَخَلَ فَسَأَلْتُ بِلَالًا أَيْنَ صَلَّى رَسُولُ اللهِ ﷺ؟ فَقَالَ بَيْنَ الْعَمُودَيْنِ الْمُقَدَّمَيْنِ وَنَسِيتُ أَنْ أَسْأَلَهُ كَمْ صَلَّى  

[Machine] "The Prophet ﷺ entered the Kaaba with Bilal, Usama, and Uthman, and the door was pushed shut behind them. I came and sat on the ground and they stayed for a while. When the Messenger of Allah ﷺ came out, I climbed the stairs and entered the house. I asked, 'Where did the Prophet ﷺ pray?' They replied, 'Here.' And I forgot to ask how many units he prayed."  

«دَخَلَ النَّبِيُّ ﷺ الْكَعْبَةَ وَمَعَهُ بِلَالٌ وَأُسَامَةُ وَعُثْمَانُ وَقَدْ أَجَافَ عَلَيْهِمُ الْبَابَ» فَجِئْتُ فَقَعَدْتُ بِالْأَرْضِ فَمَكَثُوا فِيهِ مَلِيًّا فَلَمَّا خَرَجَ رَسُولُ اللهِ ﷺ رَقِيتُ الدَّرَجَ فَدَخَلْتُ الْبَيْتَ فَقُلْتُ أَيْنَ صَلَّى النَّبِيُّ ﷺ؟ قَالُوا «هَهُنَا» وَنَسِيتُ أَنْ أَسْأَلَ كَمْ صَلَّى