Exodus 30:12-14

12‘When you count the number of the Israelites, each person must pay the Lord a price for his life. Everyone must do this at the time when you count them. Then no bad illness will happen to them as you count them.

13Each person that you count must give six grams of silver. That is the proper weight that they use in the tabernacle. The silver is an offering to the Lord.

14You must count every person who is 20 years old or more. Each person must offer his gift to the Lord.