Musnad Ahmad 5:383

Abdullah narrated to us, Abu al-Sha’tha’ Ali ibn al-Hasan ibn Sulayman narrated to me, Abu Khalid al-Ahmar Sulayman ibn Hayyan narrated to us, from Hajjaj, from Uthman, from Abu Abdullah al-Makki, from Nafi’ ibn Jubayr ibn Mut’im, who said: Ali was asked about the description of the Prophet, may Allah bless him and grant him peace, and he said: "He was neither short nor tall. His complexion was mixed with redness. He had beautiful, wavy hair. He was large-jointed. He had thick palms and feet. He had a large head. He had a long line of hair [extending from his chest to his navel]. When he walked, he leaned forward as if he were descending from a slope. I have not seen anyone like him before him nor after him, may Allah bless him and grant him peace."