Exodus 30:13-15

13Each person who is counted must give a small piece of silver as a sacred offering to the Lord. (This payment is half a shekel, based on the sanctuary shekel, which equals twenty gerahs.)

14All who have reached their twentieth birthday must give this sacred offering to the Lord.

15When this offering is given to the Lord to purify your lives, making you right with him, the rich must not give more than the specified amount, and the poor must not give less.