The LORD also said to Moses,
“Take the Levites in place of all the firstborn of Israel, and the livestock of the Levites in place of their livestock. The Levites are to be mine. I am the LORD.
References for Numbers 3:45
To redeem the 273 firstborn Israelites who exceed the number of the Levites,
References for Numbers 3:46
collect five shekels for each one, according to the sanctuary shekel, which weighs twenty gerahs.
References for Numbers 3:47