Exodus 30:12 - Matthew Poole's English Annotations on the Holy Bible

A ransom for his soul; a certain price for the redemption of their lives; whereby they acknowledge the right and power which God had over their lives, and that they had forfeited them by their sins, and that it was God's mercy to continue their lives to them. When thou numberest them, to wit, upon any just occasion, either now in the wilderness, or afterwards. It may seem that this payment was neither to be made at this time only, as some would have it; nor yet every year, as Josephus and others affirm, because it is not said to be a perpetual statute, as other things of constant observance are, but upon any eminent occasions, when the service of the tabernacle (which is the end and use of this collection) or temple required it, as may he gathered from 2 Kings 12:4, compared with 2 Chronicles 24:6. Compare Nehemiah 10:32 Matthew 17:24. And as now it was employed in the building of the tabernacle, so afterwards it might be laid out upon the repairs or other services of it.