I came and behold, Allah's Messenger (ﷺ) was staying on a Mashroba (attic room) and a black slave of Allah's Messenger (ﷺ) 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.

Sahih al-Bukhari Book 95, Hadith 17