Musnad Ahmad 31:537

'Attab narrated to us, 'Abdullah narrated to us, Ibn Lahi'ah informed us, Yazid ibn Abi Habib narrated to me, from Yazid ibn Abi Sa'id, the freed slave of al-Mahri, from his father, from Abu Sa'id al-Khudri, that the Prophet (peace and blessings of Allah be upon him) sent an expedition to Banu Lihyan. He said: Meaning, let one man from every two men go forth. And he said to the one who remained behind: "Whichever of you remains behind the one who goes out, looking after his family and wealth with goodness, he shall have the like of half the reward of the one who goes out."