Commentators like Ellicott and Gill note that this law is a repetition from Exodus 13. Its inclusion here is significant because it's part of the covenant renewal after the golden calf incident. The rules for redeeming a donkey with a lamb, or redeeming a firstborn son, re-establish the foundational principle of substitution: what belongs to God must be consecrated or 'bought back,' a central concept in Israel's relationship with Him.