Exodus 30:12-13
12
"When you take a census of the children of Israel, according to those who are numbered among them, then each man shall give a ransom for his soul to Yahweh, when you number them; that there be no plague among them when you number them.
13
They shall give this, everyone who passes over to those who are numbered, half a shekel after the shekel of the sanctuary; (the shekel is twenty gerahs;) half a shekel for an offering to Yahweh.