Musnad Ahmad 1018:26

Husayn ibn Muhammad narrated to us, Sulayman ibn Qarm narrated to us, from al-Ash'ath, from his paternal aunt Rahm, from 'Ubaydah ibn Khalaf, who said: I came to Medina while I was a young man, wearing a striped garment of mine that I was dragging. A man caught up with me and poked me with a small stick he had with him, then said: "If you were to raise your garment, it would be more lasting and cleaner." I turned around, and it was the Messenger of Allah, peace and blessings of Allah be upon him. I said: "O Messenger of Allah, it is only a striped garment." He said: "Even if it is a striped garment, is there not an example for you in me?" I looked at his lower garment, and it was above the ankles and below the calf muscle.