Musnad Ahmad 31:123

Harun ibn Ma'ruf narrated to us, Ibn Wahb narrated to us, he said: 'Amr informed me, from Yazid ibn Abi Habib, from Yazid ibn Abi Sa'id, the freed slave of al-Mahri, from his father, 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, [ordering] that from every two men, one should go out. Then he said to the one who remained behind: "Whoever of you looks after the one who went out in his family and his wealth with goodness, he shall have the like of half the reward of the one who went out."