Musnad Ahmad 5:785

Muhammad ibn Ubayd narrated to us, Mukhtar ibn Nafi‘ al-Tammar narrated to us, from Abu Matar, that he saw Ali approach a young boy and buy a shirt from him for three dirhams. He wore it, and it reached from his wrists to his ankles. He said while wearing it: "Praise be to Allah, who has provided me with clothing with which I may adorn myself among the people and cover my nakedness." It was said to him: "Is this something you are narrating from yourself, or from the Prophet of Allah, may Allah bless him and grant him peace?" He said: "This is something I heard the Messenger of Allah, may Allah bless him and grant him peace, saying when putting on clothing: 'Praise be to Allah, who has provided me with clothing with which I may adorn myself among the people and cover my nakedness.'"