Covering private parts, a man should not be seen naked

 Jabir bin ´Abdullah narrated: While the Messenger of Allah salla alayhi wa sallam was carrying stones (alone) with the people of Makkah for (the building of) the Ka´bah wearing his lzar (lower garment), his uncle Al-´Abbas said to him, ´´O my nephew! (It would be better) if you undo your lzar and put it over your shoulders underneath the stones.´´ So he undid his lzar and put it over his shoulders, but he fell unconscious and since then he had never been seen naked.