Sahih Muslim Book 1 – Hadith 5-6

Abu Huraira reported:

One day the Messenger of Allah (ﷺ) appeared before the public so a man came to him and then said: Prophet of Allah, what is Iman? Upon this he (the Holy Prophet) replied: That you affirm your faith in Allah, His angels, His Books, His meeting, His Messengers and that you affirm your faith in the Resurrection hereafter. He said: Messenger of Allah, what is al-Islam? He replied: Al-Islam is that you worship Allah and do not associate anything with Him and you establish obligatory prayer and you pay the obligatory alms (Zakat) and you observe the fast of Ramadan. He said: Messenger of Allah, what is al-Ihsan? He replied: That you worship Allah as if you are seeing Him, and for if you fail to see Him. He said: Messenger of Allah, when is the Hour (of Doom)? He replied: The one who is asked about it is no better informed than the inquirer, however I will narrate some of its signs to you. When the slave-girl will give birth to her master, then that is from its signs. When the naked, barefooted would become the chiefs of the people, then that is from its signs. When the shepherds of the black (camels) would exult themselves in buildings, then that is from its signs. (The Hour is) Among one of the five which no one knows but Allah. Then he recited (the verse): "Verily Allah! with Him alone is the knowledge of the Hour and He it is Who sends down the rain and knows that which is in the wombs. And no soul knows what it shall earn tomorrow, and a soul knows not in what land it shall die. Verily Allah is Knowing, Aware." He (Abu Huraira) said: Then the person turned back and went away. The Messenger of Allah (ﷺ) said: Bring that man back to me. They went to bring him back, but they saw nothing there. Upon this the Messenger of Allah remarked: he was Gabriel, who came to teach the people their religion. (Sahih Muslim Book 1 – Hadith 5)

This hadith is narrated to us on the authority of Muhammad b. 'Abdullah b. Numair, on the authority of Muhammad b. Bishr, on the authority of Abd Hayyan al-Taymi with the exception that in this narration (instead of the words (Iza Waladat al'amah rabbaha), the words are (Iza Waladat al'amah Ba'laha), i, e, when slave-girl gives birth to her master. (Sahih Muslim Book 1 - Hadith 6)