Numbers 3:45-48

“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. And as the redemption price for the 273 of the firstborn of the people of Israel, over and above the number of the male Levites, you shall take five shekels per head; you shall take them according to the shekel of the sanctuary (the shekel of twenty gerahs), and give the money to Aaron and his sons as the redemption price for those who are over.”