Sahih Bukhari

Narrated Abu Huraira:The Prophet (ﷺ) said, ""Between the two blowing of the trumpet there will be forty."" The people said, ""O Abu Huraira! Forty days?"" I refused to reply. They said, ""Forty years?"" I refused to reply and added: Everything of the human body will decay except the coccyx bone (of the tail) and from that bone Allah will reconstruct the whole body