Musnad Abu Ya'la al-Mawsili 42:84

Abu Musa Muhammad ibn al-Muthanna narrated to us, Ibn Abi ‘Adi narrated to us, from Sa‘id, Sulayman al-Naji informed us, from Abu al-Mutawakkil al-Naji, from Abu Sa‘id al-Khudri: That the Prophet of Allah, may Allah bless him and grant him peace, prayed with his companions. A man came, and the Prophet of Allah, may Allah bless him and grant him peace, said, "Who will trade for this [man] and pray with him?" He said: So a man prayed with him.