Messenger of Allah ﷺ entered Makkah through its upper part and he was riding his she-camel. Usãma bin Zaid was his Companion-rider behind him (on the same she-camel). In his company were Bilãl and 'Uthmãn bin Talha, who was one of the Al-Hajabah (who keep the key of the gate of the Ka'bah). When he made his she-camel kneel down in the Mosque (i.e., Al-Masjid al-Haram), he ordered him (i.e., 'Uthman) to bring the key of the Ka'bah. Then Messenger of Allah ﷺ entered the Ka'bah along with 'Usãma bin Zaid, Bilãl and 'Uthmãn bin Talha, and he stayed in it for a long period and then came out. The people rushed (to get in) and ʿAbdullãh bin 'Umar was the first to enter and he found Bilãl standing behind the door. Ibn ʿUmar asked Bilãl, "Where did Messenger of Allah ﷺ offer the Salat (prayer)?" Bilãl showed him the place where he ﷺ had offered Salat (prayer). ʿAbdullah later on said, "I forgot to ask Bilãl how many prostrations (i.e., Rak'a) the Prophet offered."  

أَنَّ رَسُولَ اللَّهِ ﷺ أَقْبَلَ يَوْمَ الْفَتْحِ مِنْ أَعْلَى مَكَّةَ عَلَى رَاحِلَتِهِ مُرْدِفًا أُسَامَةَ بْنَ زَيْدٍ وَمَعَهُ بِلاَلٌ وَمَعَهُ عُثْمَانُ بْنُ طَلْحَةَ مِنَ الْحَجَبَةِ حَتَّى أَنَاخَ فِي الْمَسْجِدِ فَأَمَرَهُ أَنْ يَأْتِيَ بِمِفْتَاحِ الْبَيْتِ فَدَخَلَ رَسُولُ اللَّهِ ﷺ وَمَعَهُ أُسَامَةُ بْنُ زَيْدٍ وَبِلاَلٌ وَعُثْمَانُ بْنُ طَلْحَةَ فَمَكَثَ فِيهِ نَهَارًا طَوِيلاً ثُمَّ خَرَجَ فَاسْتَبَقَ النَّاسُ فَكَانَ عَبْدُ اللَّهِ بْنُ عُمَرَ أَوَّلَ مَنْ دَخَلَ فَوَجَدَ بِلاَلاً وَرَاءَ الْبَابِ قَائِمًا فَسَأَلَهُ أَيْنَ صَلَّى رَسُولُ اللَّهِ ﷺ فَأَشَارَ لَهُ إِلَى الْمَكَانِ الَّذِي صَلَّى فِيهِ قَالَ عَبْدُ اللَّهِ فَنَسِيتُ أَنْ أَسْأَلَهُ كَمْ صَلَّى مِنْ سَجْدَةٍ  

Messenger of Allah ﷺ came to Mecca through its higher region on the day of the Conquest (of Mecca) riding his she-camel on which Usama was riding behind him. Bilal and ʿUthman bin Talha, one of the servants of the Kaʿba, were also accompanying him till he made his camel kneel in the mosque and ordered the latter to bring the key of the Kaʿba. He opened the door of the Kaʿba and Messenger of Allah ﷺ entered in the company of Usama, Bilal and ʿUthman, and stayed in it for a long period. When he came out, the people rushed to it, and ʿAbdullah bin ʿUmar was the first to enter it and found Bilal standing behind the door. He asked Bilal, "Where did the Prophet ﷺ offer his prayer?" He pointed to the place where he had offered his prayer. ʿAbdullah said, "I forgot to ask him how many rakʿat he had performed." (Using translation from Bukhārī 2988)   

أَنَّ رَسُولَ اللهِ ﷺ أَقْبَلَ يَوْمَ الْفَتْحِ مِنْ أَعْلَى مَكَّةَ عَلَى رَاحِلَتِهِ فَرَدَفَ أُسَامَةَ بْنَ زَيْدٍ وَمَعَهُ بِلَالٌ وَمَعَهُ عُثْمَانُ بْنُ طَلْحَةَ مِنَ الْحَجَبَةِ حَتَّى أَنَاخَ فِي الْمَسْجِدِ فَأَمَرَهُ أَنْ يَأْتِيَ بِمِفْتَاحِ الْبَيْتِ فَفَتَحَ وَدَخَلَ رَسُولُ اللهِ ﷺ وَمَعَهُ أُسَامَةُ وَبِلَالٌ وَعُثْمَانُ فَمَكَثَ فِيهَا نَهَارًا طَوِيلًا ثُمَّ خَرَجَ فَاسْتَبَقَ النَّاسُ فَكَانَ عَبْدُ اللهِ بْنُ عُمَرَ أَوَّلَ مَنْ دَخَلَ فَوَجَدَ بِلَالًا وَرَاءَ الْبَابِ قَائِمًا فَسَأَلَهُ أَيْنَ صَلَّى رَسُولُ اللهِ ﷺ؟ فَأَشَارَ لَهُ إِلَى الْمَكَانِ الَّذِي صَلَّى فِيهِ قَالَ عَبْدُ اللهِ فَنَسِيتُ أَنْ أَسْأَلَهُ كَمْ صَلَّى مِنْ سَجْدَةٍ؟