Numbers 3:11-13 - Arthur Peake's Commentary on the Bible

The Relation of the Levites to the People. The Levites are here considered as dedicated to Yahweh in lieu of the first-born of Israel to whom He had a claim, and for whom no redemption money had been paid in the past (in the future every first-born child is to be redeemed by the payment of 5 shekels (Numbers 18:16)). Yahweh's claim is here based on the sparing of the Hebrew children at the Exodus (Exodus 13:11-15); but elsewhere all first-born creatures are regarded as Yahweh's (Exodus 22:29 f; Exodus 34:19 f.); Perhaps originally supernatural qualities were associated with the firstborn (in whom, if a family were thought to be descended from a Divine ancestor, the Divine strain might seem to be strongest, cf. Genesis 49:3 *), so that such were held to be more than ordinarily sacred; and if a sacrifice were required, the holiest victim would appear the most appropriate (cf. Genesis 22:2; 2 Kings 3:27; Ezekiel 20:26; Micah 6:7).