Exodus 30:12-13

30:12 “When you take a census of the Israelites according to their number, then each man is to pay a ransom for his life to the Lord when you number them, so that there will be no plague among them when you number them. 30:13 Everyone who crosses over to those who are numbered is to pay this: a half shekel according to the shekel of the sanctuary (a shekel weighs twenty gerahs). The half shekel is to be an offering to the Lord.