Narrated Anas:
that Abu Bakr narrated to him, he said: "While were in the cave, I said to the Prophet (ﷺ): 'If one of them were to look down at his feet, then he would see us under his feet.' So he said: 'O Abu Bakr! What do you think about two, the third of whom is Allah?'" (PT)
English reference (PT): Vol. 5, Book 44, Hadith 3096 (PT)
Arabic reference (PT): Book 47, Hadith 3379 (PT)