Musnad Ahmad 27:1277

Abdullah ibn al-Walid narrated to us, Sufyan narrated to us, from Abdullah ibn Muhammad ibn Aqil, who said: I heard Ibn Umar saying: The Messenger of Allah (peace and blessings of Allah be upon him) clothed me in a Qibti garment, and he clothed Usama in a garment of silk. He said: Then he looked and saw that I had let my garment hang low (isbal). So he came and took hold of my shoulder and said: "O Ibn Umar, everything of clothing that touches the ground is in the Fire." He said: So I saw Ibn Umar thereafter wearing his lower garment up to the middle of his shin.