Abu Hurairah (RA) reported Allah's Messenger (ﷺ) as saying: Between the two blowiings of the trumpet (there would be an interval of forty). They said: Abu Hurairah (RA) , do you mean forty days? He said: I cannot say anything. They said: Do you mean fortv 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.
Hadith Referenceصحيح مسلم / كتاب الفتن وأشراط الساعة / 2955
Abu Hurairah (RA) reported Allah's Messenger (ﷺ) as saying: The earth would consume every son of Adam ؑexcept his spinal chord from which his body would be reconstituted (on the Day of Resurrection).
Hadith Referenceصحيح مسلم / كتاب الفتن وأشراط الساعة / 2955
Abu Hurairah (RA) reported so many ahadith from Allah's Apostle (ﷺ) and amongst these one was this that Allah's Messenger (ﷺ) said: There is a bone in the human being which the earth would never consume and it is from this that new bodies would be reconstituted (on the Day of Resurrection). They said: Allah's Messenger, which bone is that? Thereupon he said: It is the spinal bone.
Hadith Referenceصحيح مسلم / كتاب الفتن وأشراط الساعة / 2955