Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrated: I went to the Messenger of Allah (peace and blessings be upon him) while he was in a room that was like a pigeon coop, and he was sleeping on a mat that had left marks on his side. So I wept. He (peace and blessings be upon him) said: "O Abdullah, what makes you weep?" I said: O Messenger of Allah, Chosroes and Caesar walk upon fine silk-wool (khazz), silk and brocade, while you sleep on this mat that has left marks on your side. He (peace and blessings be upon him) said: "Do not weep, O Abdullah; for them is this world and for us is the Hereafter. What have I to do with this world? The likeness of me and this world is only that of a rider who stopped beneath a tree, then moved on and left it."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10289