Numbers 3:45

45.Take the Levites instead of all the first-born The compensation of which I have spoken follows; for, since the complete portion of God was not found in the tribe of Levi, it must needs be supplied from elsewhere. Since, then, the Levites, infants as well as men, were less by two hundred and seventy-three than the first-born of the twelve tribes of Israel, God required that five shekels of the sanctuary should be paid for every head. We have elsewhere seen that the shekel of the sanctuary was double, amounting to two ordinary ones.