Silsilat al-Ahadith al-Sahihah

Abu Sa'id al-Khudri (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings of Allah be upon him) said: "When our Lord will uncover His Shin, then every believing man and woman will prostrate to Him, but those who used to prostrate (in the world) for showing off and for fame will remain (standing). Each of them will try to prostrate, but his back will become a single plank (stiff and unable to bend)."