Exodus 30:11-16:

And the LORD spake unto Moses, saying,
When thou takest the sum of the children of Israel after their number, then shall they give every man a ransom for his soul unto the LORD, when thou numberest them; that there be no plague among them, when thou numberest them.
This they shall give, every one that passeth among them that are numbered, half a shekel after the shekel of the sanctuary; (a shekel is twenty gerahs:) an half shekel shall be the offering of the LORD.
Every one the passeth among them that are numbered, from twenty years old and above, shall give an offering unto the LORD.
The rich shall not give more, and the poor shall not give less than half a shekel, when they give an offering unto the LORD, to make an atonement for your souls.
And thou shalt take the atonement money of the children of Israel, and shall appoint it for the service of the tabernacle of the congregation; that it may be a memorial unto the children of Israel before the LORD, to make an atonement for your souls.

Notes on Exodus 30:11-16:

By making the ransom the same amount for everyone, I believe that God shows us here that the rich and the poor are both worth the same in His eyes.  In today’s world, the people would howl that this is a “regressive” tax that makes the poor pay a higher percentage of their income than the rich have to pay, so it’s a good thing that modern politicians weren’t around back then to get the people to rebel against God’s mandate.  The value of your soul has nothing to do with your financial condition, and atonement for souls was the issue here.

See also:

Healing and Atonement
Healing and Giving