Sunan at-Tirmithiy كتاب الزهد باب [ ما لى وما للدنيا ]
The Messenger of God, peace and blessings of God be upon him, once slept on a mat made of palm-leaves that left a mark on his side when he woke up. So we said, "Messenger of God, if only we could get you a bed!" He replied, "What have I to do with this world? I am in this world but a passenger who rests under the shade of a tree, then departs leaving it behind." Click on ḥadīth to read more