Sahih al-Bukhari, Hadith 7263 ⓘ
Narrated `Umar: I came and behold, Allah's Messenger was staying on a Mashroba (attic room) and a black slave of Allah's Messenger was at the top if its stairs. I said to him, "(Tell the Prophet) that here is `Umar bin Al- Khattab (asking for permission to enter)." Then he admitted me.
حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُلَيْمَانُ بْنُ بِلاَلٍ، عَنْ يَحْيَى، عَنْ عُبَيْدِ بْنِ حُنَيْنٍ، سَمِعَ ابْنَ عَبَّاسٍ، عَنْ عُمَرَ ـ رضى الله عنهم ـ قَالَ جِئْتُ فَإِذَا رَسُولُ اللَّهِ صلى الله عليه وسلم فِي مَشْرُبَةٍ لَهُ، وَغُلاَمٌ لِرَسُولِ اللَّهِ صلى الله عليه وسلم أَسْوَدُ عَلَى رَأْسِ الدَّرَجَةِ فَقُلْتُ قُلْ هَذَا عُمَرُ بْنُ الْخَطَّابِ فَأَذِنَ لِي.
also referenced under: Book 95, Hadith 17 (In-Book) & Volume 9, Book 91, Hadith 368 (USC-MSA)