Musnad Ahmad 1234:4

Yahya ibn Sa'id narrated to us, from Isma'il, who said: Qays narrated to us, from Khabbab, who said: We complained to the Messenger of Allah (peace and blessings of Allah be upon him) while he was reclining on a cloak in the shade of the Ka'bah. We said: "Will you not seek help from Allah, the Almighty and Majestic, for us?" or he said: "Will you not pray for our victory?" He said: "A man among those who were before you would be taken, and a pit would be dug for him in the earth. Then a saw would be brought and placed upon his head, and he would be split into two halves, yet that would not turn him away from his religion. And he would be combed with iron combs, tearing away the flesh or nerves from beneath his bones, yet that would not turn him away from his religion. By Allah, Allah will surely complete this matter until a traveler journeys from Medina to Hadramawt, fearing none but Allah, the Almighty and Majestic, and [fearing for] the wolf upon his sheep; but you are impatient."