Numbers 3:44-51

44 Then the Lord spoke to Moses, saying:
45 Accept the Levites as substitutes for all the firstborn among the Israelites, and the livestock of the Levites as substitutes for their livestock; and the Levites shall be mine. I am the Lord.
46 As the price of redemption of the two hundred seventy-three of the firstborn of the Israelites, over and above the number of the Levites,
47 you shall accept five shekels apiece, reckoning by the shekel of the sanctuary, a shekel of twenty gerahs.
48 Give to Aaron and his sons the money by which the excess number of them is redeemed.
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 Israelites he took the money, one thousand three hundred sixty-five shekels, reckoned by the shekel of the sanctuary;
51 and Moses gave the redemption money to Aaron and his sons, according to the word of the Lord, as the Lord had commanded Moses.
New Revised Standard Version Bible, copyright 1989, Division of Christian Education of the National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved.