Exodus 30:11-13

The LORD said to Moses, “When you count the people of Israel, every person must buy back his life from the LORD so that no terrible things will happen to the people when you number them. Every person who is counted must pay one-fifth of an ounce of silver. (This is set by using one-half of the Holy Place measure, which weighs two-fifths of an ounce.) This amount is a gift to the LORD.