Musnad Ahmad 217:2

'Abd al-Razzaq narrated to us, he said: Ma'mar informed us, from al-Zuhri, from 'Urwah ibn al-Zubayr, from Karz ibn 'Alqamah al-Khuza'i, who said: A Bedouin said: "O Messenger of Allah, does Islam have an end?" He said: "Yes. Whichever household of the Arabs or the non-Arabs Allah, the Mighty and Majestic, intends good for, He introduces Islam into them." He said: "Then what, O Messenger of Allah?" He said: "Then tribulations will occur, as if they were shadows." The Bedouin said: "Nay, O Messenger of Allah." The Prophet, peace and blessings of Allah be upon him, said: "Yes, by the One in Whose hand is my soul, you will return in them as dark snakes, striking the necks of one another."