Exo 13:15, Num 3:45-51 | ESV | STEP | For when Pharaoh stubbornly refused to let us go , the Lord killed all the firstborn in the land of Egypt , both the firstborn of man and the firstborn of animals . Therefore I sacrifice to the Lord all the males that first open the womb , but all the firstborn of my sons I redeem .

Exodus 13:15

15 For when Pharaoh stubbornly refused to let us go, the ^aLord killed all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of animals. Therefore I sacrifice to the Lord all the males that first open the womb, but ^ball the firstborn of my sons I redeem.’

Numbers 3:45-51

45 ^c“Take the Levites instead of all the firstborn among the people of Israel, and the cattle of the Levites instead of their cattle. The Levites shall be mine: I am the Lord. 46 And ^das the redemption price for the 273 of the firstborn of the people of Israel, over and above the number of the male Levites, 47 you shall take ^efive shekels ^{▼▼A shekel was about 2/5 ounce or 11 grams} per head; you shall take them according to ^gthe shekel of the sanctuary (the shekel of twenty gerahs ^{▼▼A gerah was about 1/50 ounce or 0.6 gram}), 48 and give the money to Aaron and his sons as the redemption price for those who are over.” 49 So Moses took the redemption money from those who were over and above those redeemed by the Levites. 50 From the firstborn of the people of Israel he took the money, ⁱ1,365 shekels, by the shekel of the sanctuary. 51 And Moses ^jgave the redemption money to Aaron and his sons, according to the word of the Lord, as the Lord commanded Moses.