1 Samuel 30:22-25

Then all the wicked and worthless men among those who went with David said, “Because they did not go with us, we will give them none of the spoil that we have recovered, except that each man may take his wife and children away and leave.” David said, “You must not do so, my brothers, with what the LORD has given us. He has kept us safe and has handed over to us the band [of Amalekites] that came against us. And who will listen to you in regard to this matter? For as is the share of him who goes down into the battle, so shall his share be who stays by the provisions and supplies; they shall share alike.” So from that day forward he made it a statute and an ordinance for Israel to this day.