Musannaf Ibn Abi Shayba 16:581

Abu Bakr narrated to us, he said: Ubayd Allah ibn Musa narrated to us, he said: Shayban narrated to us, from Ash'ath ibn Abi al-Sha'tha', he said: Sa'id ibn Jubayr narrated to me, from Ibn Abbas, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, Allah does not look at one who lets his garment trail."