Adam Clarke on 1 Samuel 30:25

He made it a statute and an ordinance for Israel - Nothing could be more just and proper than this law: he who stays at home to defend house and property, has an equal right to the booty taken by those who go out to the war. There was a practice of this kind among the Israelites long before this time; see Num 31:27; Jos 22:8; and the note on this latter verse.

Unto this day - This is another indication that this book was composed long after the facts it commemorates. See the hypothesis in the preface.