Sayyiduna Khabbab (may Allah be pleased with him) said: We complained (of our hardship) to the Messenger of Allah (peace and blessings be upon him) while he was reclining on his cloak in the shade of the Ka'bah. We said: Why do you not pray to Allah Almighty for us? Why do you not ask Allah to help us? His (peace and blessings be upon him) blessed face turned red and he sat up straight. Then he (peace and blessings be upon him) said: "By Allah! Among the (believing) people before you, a man would be seized and a pit would be dug for him. Then a saw would be placed on his head and he would be cut into two pieces, yet even this would not turn him away from his religion; and he would be raked with iron combs between his sinews and his flesh, yet even this torment would not keep him from his religion. And Allah Almighty will most certainly make this religion prevail and complete it, until a rider among you will travel from San'a to Hadramawt fearing no one but Allah, nor (fearing) the wolf for his sheep; but you are in a hurry."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17720