Sahih al-Bukhari 4814
صحيح البخاري#4814SahihNarrated 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 65:336