Exodus 30:11-13

Then the LORD said to Moses, “When you take the census of the Israelites, each one shall give a ransom for himself to the LORD when you count them, so that no plague will come on them when you number them. [Rom 8:1-4] This is what everyone who is counted shall give [as he joins those already counted]: a half shekel, according to the sanctuary shekel (the shekel is twenty gerahs); a half shekel as a contribution to the LORD.