Exodus 13:12-13 NKJV
that you shall set apart to the LORD all that open the womb, that is, every firstborn that comes from an animal which you have; the males shall be the LORD’s. But every firstborn of a donkey you shall redeem with a lamb; and if you will not redeem it, then you shall break its neck. And all the firstborn of man among your sons you shall redeem.
NKJV: New King James Version