Musnad Ahmad 26:27

Sufyan narrated to us, from ‘Asim, from Zirr, from ‘Abdullah, who said: We were with the Prophet, peace and blessings of Allah be upon him, in a cave, when there was revealed to him: "By the winds sent forth in succession" (Al-Mursalat). I took it from his mouth, and his mouth was moist with it. I do not know with which of them it ended: "Then in what statement after it will they believe?" (Al-Mursalat: 50), or "And when it is said to them, 'Bow [in prayer],' they do not bow" (Al-Mursalat: 48)? A snake preceded us and entered a hole. The Prophet, peace and blessings of Allah be upon him, said: "You have been protected from its evil, and it has been protected from your evil."