Exodus 30:13-16

13This shall they give — every one that passeth among them that are numbered — half a shekel after the shekel of the sanctuary, — twenty gerahs the shekel; a half shekel shall be the heave-offering for Jehovah.

14Every one that passeth among those that are numbered, from twenty years old and above, shall give the heave-offering of Jehovah.

15The rich shall not give more, and the poor shall not give less than half a shekel, when ye give the heave-offering of Jehovah, to make atonement for your souls.

16And thou shalt take the atonement-money of the children of Israel, and devote it to the service of the tent of meeting; and it shall be a memorial to the children of Israel before Jehovah, to make atonement for your souls.