Musnad Ahmad 5:626

Muhammad ibn Ja‘far narrated to us, Shu‘bah and Hajjaj narrated to us, from Shu‘bah, from Salamah ibn Kuhayl, who said: I heard Habbah al-‘Arani say: I heard ‘Ali say: "I am the first person who prayed with the Messenger of Allah, may Allah bless him and grant him peace."