Numbers 3:46-48

46And for those that are to be redeemed of the two hundred and threescore and thirteen of the firstborn of the children of Israel, which are more than the Levites;

47Thou shalt even take five shekels apiece by the poll, after the shekel of the sanctuary shalt thou take them: (the shekel is twenty gerahs:)

48And thou shalt give the money, wherewith the odd number of them is to be redeemed, unto Aaron and to his sons.