Sahih Muslim Book 41, Hadith Number 7055.

Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: Between the two blowing of the trumpet (there would be an interval of forty). They said: Abu Huraira, do you mean forty days? He said: I cannot say anything. They said: Do you mean forty months? He said: I cannot say anything They said: Do you mean forty years? He said: I cannot say anything. Then Allah would cause the water to, descend from the sky and they (people) will sprout like vegetable The only thing in a man which would not decay would be one bone (spinal chord) from which the whole frame would be reconstituted on the Day of Resurrection.