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.

“There is no part of man that will not disintegrate, apart from a single bone at the base of the coccyx, from which he will be recreated on the Day of Resurrection.”

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.

`Uqba said to Hudhaifa, "Won't you narrate to us what you heard from Allah's Messenger (ﷺ) ?" Hudhaifa said, "I heard him saying, 'Death approached a man and when he had no hope of surviving, he said to his family, 'When I die, gather for me much wood and build a fire (to burn me),. When the fire has eaten my flesh and reached my bones, take the bones and grind them and scatter the resulting powder in the sea on a hot (or windy) day.' (That was done.) But Allah collected his particles and asked (him), 'Why did you do so?' He replied, 'For fear of You.' So Allah forgave him." Narrated `Abdu Malik: As above, saying, "On a windy day."

“Breaking the bones of the deceased is like breaking his bones when he is alive.”