Narrated 'Abdullãh bin 'Umar (ra):Allah's Messenger (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 Allah's Messenger (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 `Abdullãh bin 'Umar was the first to enter and he found Bilãl standing behind the door. Ibn `Umar asked Bilãl, "Where did Allah's Messenger (ﷺ) offer the Salat (prayer)?" Bilãl showed him the place where he (ﷺ) had offered Salat (prayer). `Abdullah later on said, "I forgot to ask Bilãl how many prostrations (i.e., Rak'a) the Prophet offered."
وَقَالَ اللَّيْثُ حَدَّثَنِي يُونُسُ، قَالَ أَخْبَرَنِي نَافِعٌ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ـ رضى الله عنهما ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم 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 صلى الله عليه وسلم 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 صلى الله عليه وسلم فَأَشَارَ لَهُ إِلَى الْمَكَانِ الَّذِي صَلَّى فِيهِ. قَالَ عَبْدُ اللَّهِ فَنَسِيتُ أَنْ أَسْأَلَهُ كَمْ صَلَّى مِنْ سَجْدَةٍ
Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) • Hadith 322