It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that Umar bin al-Khattab (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him) while he (peace and blessings be upon him) was on a mat that had left marks on his (peace and blessings be upon him) side. He said: O Messenger of Allah! If only you would take a bedding softer than this (it would be better). He (peace and blessings be upon him) said: "What have I to do with this world? By the One in whose Hand is my soul! The likeness of me and this world is only that of a rider travelling on a summer day, who then rests in the shade of a tree for an hour of the day, then moves on and leaves it."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11848