Exodus 13:13

And every firstling of an ass thou shalt redeem with a lamb; and if thou wilt not redeem it, then thou shalt break his neck: and all the firstborn of man among thy children shalt thou redeem.

Cross-reference

Exodus 34:20 repeats the redemption rule for a donkey's firstborn—redeem with a lamb or break its neck—same stipulation.

Numbers 3:46-51 directly applies the same redemption principle to Israel's firstborn, with Levites as substitutes.

Numbers 18:15-17 elaborates the same redemption law, specifying the price for firstborn sons and rules for unclean animals.

Numbers 18:16 specifies the five shekel redemption price for firstborn sons, directly clarifying this law.

Leviticus 27:26 declares firstborn animals already belong to the Lord, reinforcing the consecration principle here.