صحيح البخاري

Narrated Abu Bakr:

I was with the Prophet (ﷺ) in the Cave. When I raised my head, I saw the feet of the people. I said, "O Allah's Messenger! If some of them should look down, they will see us." The Prophet (ﷺ) said, "O Abu Bakr, be quiet! (For we are) two and Allah is the Third of us."