Cross reference
Numbers 3:46
46 And for the redemption of the two hundred and threescore and thirteen of the first-born of the children of Israel, that are over and above `the number of' the Levites,
Exodus 13:13
13 And every firstling of an ass thou shalt redeem with a lamb; and if thou wilt not redeem it, then thou shalt break its neck: and all the first-born of man among thy sons shalt thou redeem.
Numbers 18:15-16
15 Everything that openeth the womb, of all flesh which they offer unto Jehovah, both of man and beast shall be thine: nevertheless the first-born of man shalt thou surely redeem, and the firstling of unclean beasts shalt thou redeem.
16 And those that are to be redeemed of them from a month old shalt thou redeem, according to thine estimation, for the money of five shekels, after the shekel of the sanctuary (the same is twenty gerahs).