Exodus 30:13-16

13This 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.

14Everyone who is counted, from twenty years old and over, [as he joins those already counted], shall give this contribution to the Lord.

15The rich shall not give more and the poor shall not give less than half a shekel, when you give this contribution to the Lord to make atonement for yourselves.

16You shall take the atonement money from the Israelites and use it [exclusively] for the service of the Tent of Meeting, so that it may be a memorial for the Israelites before the Lord, to make atonement for yourselves.”