Sahih (Sahih Muslim)
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا الْمُغِيرَةُ، - يَعْنِي الْحِزَامِيَّ - عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " كُلُّ ابْنِ آدَمَ يَأْكُلُهُ التُّرَابُ إِلاَّ عَجْبَ الذَّنَبِ مِنْهُ خُلِقَ وَفِيهِ يُرَكَّبُ " .
Abu Huraira reported Allah's Messenger (ﷺ) as saying:The earth would consume all of the son of Adam except his tailbone. From it he was created, and from it he will be recreated (on the Day of Resurrection)