Numbers 3:44-51

Then the LORD spoke to Moses, saying, “Take the Levites [for Me] instead of all the firstborn among the sons of Israel, and the cattle of the Levites instead of their cattle. And the Levites shall be Mine. I am the LORD. For the ransom (redemption price) of the 273 of the firstborn of the Israelites who outnumber the Levites, you shall take five shekels apiece, per head, you shall take them in terms of the sanctuary shekel (the shekel is twenty gerahs), and give the money, the ransom (redemption price) of those who outnumber the Levites to Aaron and to his sons.” So Moses took the ransom (redemption) money from those who were in excess, beyond those ransomed by the Levites; from the firstborn of the Israelites he took the money in terms of the sanctuary shekel, 1,365 shekels. Then Moses gave the ransom money to Aaron and to his sons at the command of the LORD, just as the LORD had commanded Moses.