It was narrated that Abdullah bin Mas'ood (رضي الله عنه) said.
When we were on our way back after the campaign of al-Hudaibiyah, the Messenger of Allah (ﷺ) said: "who will guard us tonight?” Abdullah said: I said: I will. He said: “You will fall asleep." Then he repeated it "who will guard us tonight?” I said: I will. That happened several times. I said: I will, O Messenger of Allah. He said: "So you will guard us then." I guarded them until, as morning approached, the words of the Messenger of Allah (ﷺ), "You will fall asleep,” caught up with me and I fell asleep. And we did not wake up until we felt the heat of the sun on our backs. Then The Messenger of Allah (ﷺ) got up and did what he used to do of wudoo’ and praying the two (Sunnah) rak'ahs of Fajr, then he led us in praying Fajr. When he had finished, he said: If Allah, may He be glorified and exalted, had willed that you should not sleep (and miss it), you would not have fallen asleep. But He willed that you should (set an example) for those who come after you. This is what one who falls asleep or forgets should do." Then the she-camel of the Messenger of Allah (ﷺ) and the people's camels had scattered, so the people set out looking for them, and they brought their camels except the she-camel of the Messenger of Allah (ﷺ). 'Abdullah (رضي الله عنه) said: The Messenger of Allah (ﷺ) said to me: "Go and look in that direction." So I went where he told me and I sound that its reins had got caught on a tree and could only be undone by hand. So I brought it to the Prophet (ﷺ) and said: O Messenger of Allah, by the One Who sent you with the truth as a Prophet, I found its reins caught on a tree and they could only be undone by hand. Then Soorat al-Fath, “Verily, we have given you (O Muhammad (ﷺ)) a manifest victory.” (al-Fath 48:1), was revealed to the Messenger of Allah (ﷺ).