Musannaf Ibn Abi Shayba 3:803

Yahya ibn Sa'id narrated to us, from Sufyan, from Uthman ibn al-Mughirah, from Salim ibn Abi al-Ja'd, from Ibn al-Hanafiyyah, that Ali said: "There is no harm in praying in a single garment," or "Pray in a single garment."