Numbers 3:44-51

The LORD also said to Moses, “Take the Levites instead of all the firstborn sons of the Israelites, and take the animals of the Levites instead of the animals of the other people. The Levites are mine. I am the LORD. Since there are 273 more firstborn sons than Levites, collect two ounces of silver for each of the 273 sons. Use the measure as set by the Holy Place, which is two-fifths of an ounce. Give the silver to Aaron and his sons as the payment for the 273 Israelites.” So Moses collected the money for the people the Levites could not replace. From the firstborn of the Israelites, he collected thirty-five pounds of silver, using the measure set by the Holy Place. Moses obeyed the command of the LORD and gave the silver to Aaron and his sons.