Full Sharh — Riyad as-Salihin 1157
وعنه عن النبي صلى الله عليه وسلم قال: " بين النفختين أربعون" قالوا: يا أبا هريرة أربعون يوماً؟ قال: أبيت، قالوا: أربعون سنة؟ قال: أبيت، قالوا: أربعون شهراً؟ قال: أبيت" ويبلى كل شئ من الإنسان إلا عجب ذنبه، فيه يركب الخلق، ثم ينزل الله من السماء ماء، فينبتون كما ينبت البقل" ((متفق عليه)).
English Translation
Abu Hurairah (May Allah be pleased with him) said:: The Prophet (ﷺ) said, "Between the two Blowing of the Trumpet there will be an interval of forty." The people said, "O Abu Hurairah! Do you mean forty days?" He said, "I cannot say anything." They said, "Do you mean forty years?" He said, "I cannot say anything." They said, "Do you mean forty months?" He said, "I cannot say anything. The Prophet added: 'Everything of the human body will perish except the last coccyx bone (end part of the spinal cord), and from that bone Allah will reconstruct the whole body. Then Allah will send down water from the sky and people will grow like green vegetables'.".
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Miscellaneous ahadith of Significant Values
Hadith Number
1157