Musnad Ahmad 545:1

Ya'mar ibn Bishr narrated to us, he said: Abdullah narrated to us, he said: Hushaym ibn Bashir narrated to us, from Dawud ibn Amr, from Busr ibn Ubaydullah, from Samurah ibn Fatik al-Asadi, and he mentioned a hadith. He said: Ya'mar ibn Bishr narrated to us, he said: Abdullah narrated to us, he said: Hushaym narrated to us, from Dawud ibn Amr, from Busr ibn Ubaydullah, from Samurah ibn Fatik, that the Prophet, peace and blessings of Allah be upon him, said: "An excellent young man is Samurah, if he were to trim his hair and shorten his lower garment." So Samurah did that; he trimmed his hair and shortened his lower garment.