abu bakr, with whom allah is pleased, said:

‘i looked at the feet of the pagans while we were in the cave [of thawr]. i said, ‘'o prophet of allah! if anyone of them looks down at his feet he would see us!’ the messenger of allah, may allah exalt his mention, said: ‘o abu bakr! what do you think of two with whom allah, the exalted, is their third?’  (muslim #1854)