Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 185
Narrated Abu Bakr:
I was in the company of the Prophet in the cave, and on seeing the traces of the pagans, I said, "O Allah's Apostle If one of them (pagans) should lift up his foot, he will see us." He said, "What do you think of two, the third of whom is Allah?"