Nehemiah 10:32

Charge ourselves yearly with the third part of a shekel - According to the law, every one above twenty years of age was to give half a shekel to the sanctuary, which was called a ransom for their souls. See Exodus 30:11-16. But why is one third of a shekel now promised instead of the half shekel, which the law required? To this question no better answer can be given than this: the general poverty of the people, occasioned by their wars, overthrows, heavy tributes, etc., in the land of their captivity: and now on their return, having little property, it was impossible for them to give more; and we know, from the terms of the law in this case, that the poor and the rich were obliged to give alike, because it was a ransom for their souls; and the souls of the poor and the rich were of like value, and stood equally in need of redemption; for all were equally fallen, and all had come equally short of the glory of God.

Though only a third part of a shekel was given at this time, and probably for the reason above assigned, yet when the people got into a state of greater prosperity, the half shekel was resumed: for it is clear that this sum was paid in the time of our Lord, though not to the temple, but to the Roman government. Hence when those who collected this as a tribute came to our Lord, it was for the διδραχμα, didrachma, which was half a shekel; and the coin with which our Lord paid for himself and Peter was a stater, which contained exactly two half shekels. See Matthew 17:24-27.

The third part of a sheckel - This appears to have been the first occasion on which an annual payment toward the maintenance of the temple service and fabric was established. The half-shekel of the Law Exodus 30:13 was paid only at the time of a census (which rarely took place), and was thus not a recurring tax. In later times, the annual payment was raised from the third of a shekel to half a shekel Matthew 17:24.