Musnad Ahmad 908:18

Yazid narrated to us, Ismail bin Abi Khalid informed us, from Qais bin Abi Hazim, who said: We came to Khabbab bin al-Aratt to visit him, and he had been cauterized seven times on his stomach. He said: "Had the Messenger of Allah (peace and blessings of Allah be upon him) not forbidden us from praying for death, I would have prayed for it, for my illness has lasted long for me." Then he said: "Our companions who have passed on did not have their reward diminished by the world in any way, but we have acquired after them that for which we find no place except the dust." He said: He was building a wall for himself. "And the Muslim man is rewarded for all his spending, except for something he puts into the dust." He said: We complained to the Messenger of Allah (peace and blessings of Allah be upon him) while he was reclining on a cloak of his in the shade of the Kaaba. We said: "O Messenger of Allah, will you not seek victory from Allah for us?" He sat up, his face reddening, and said: "By Allah, there were those before you who would be seized, and saws would be placed upon their heads, and they would be split into two parts, yet that would not turn them away from their religion. And Allah will surely complete this matter, until a rider travels between Sana'a and Hadhramaut, fearing nothing but Allah and the wolf for his sheep."