Musnad Ahmad 31:471

'Abd al-Rahman narrated to us, Harb ibn Shaddad narrated to us, from Yahya ibn Abi Kathir, that Abu Sa'id, the freed slave of al-Mahri, narrated to him, from Abu Sa'id al-Khudri, that the Messenger of Allah (peace and blessings of Allah be upon him) sent an expedition to Banu Lihyan of Hudhayl. He said: "Let one man from every two men go forth, and the reward is between them."