Exodus 30:13 - Matthew Poole's English Annotations on the Holy Bible

The shekel of the sanctuary hath been commonly conceived to be double to the common shekel, yet divers late learned men seem more truly to judge that it was no more than the common shekel, consisting of half a crown of English money; which is called the shekel of the sanctuary, because the standard by which all shekels were to be examined was kept in the sanctuary, as afterwards the just weights and measures were kept in Christian temples, or other public places. See Leviticus 27:25 Numbers 3:47 Ezekiel 45:10-12. Add to this, that it was a part of the priest's office to look to the weights and measures, as plainly appears from 1 Chronicles 23:29. An half shekel shall be the offering; not less, lest it should be contemptible; nor more, lest it should be too burdensome for the poor.