Exodus 34:20

But the firstling of an ass thou shalt redeem with a lamb: and if thou redeem him not, then shalt thou break his neck. All the firstborn of thy sons thou shalt redeem. And none shall appear before me empty.

Cross-references

Exodus 13:15 grounds this redemption command in the Passover: the LORD spared Israel's firstborn but struck Egypt's, so we redeem our sons.

Exodus 13:2 first commands consecration of all firstborn; this verse reaffirms that law with redemption details.

Exodus 13:13 gives the same rule: redeem firstborn donkey with lamb or break its neck.

Numbers 3:45-51 details this redemption: the Levites substitute for all firstborn sons, with a monetary redemption for the surplus.

Numbers 18:15 echoes this law: firstborn of man and unclean animals must be redeemed, with the priest receiving the redeemed animals.