How can we harmonize Numbers 4:1-3 & Numbers 8:23?

Question

Numbers 4:1-3 NASB

[1]Then the Lord spoke to Moses and to Aaron, saying, [2]"Take a census of the descendants of Kohath from among the sons of Levi, by their families, by their fathers' households, [3]from thirty years and upward, even to fifty years old, all who enter the service to do the work in the tent of meeting.

Numbers 8:23-25 NASB

[23]Now the Lord spoke to Moses, saying, [24]"This is what applies to the Levites: from twenty-five years old and upward they shall enter to perform service in the work of the tent of meeting. [25]But at the age of fifty years they shall retire from service in the work and not work any more.

Emphasis added

When the census was taken of the Levite's the age restriction was thirty to fifty years who came to serve in the work of the tent meeting,but when they were consecrated & purified the age restriction seems to have changed to twenty five years & over.

How can we reconcile the supposed contradiction?

Answer 1

If you read closely, you will see that Numbers 4:1-3 specifies the age limit of Levites who will be counted in the census, whereas Numbers 8:23-25 specifies the age limits for Levitic duties.

One commentator has speculated that between the ages of 25 and 30, Levites served as assistants, but not full-fledged priests.¹ Rashi comments on 8:24:

Elsewhere (4:3) it says, “From the age of thirty.” How can this be reconciled? However, from the age of twenty-five they came to study the laws of the service; they would study for five years, and at the age of thirty they would [begin] work. From here we learn that a student who does not experience success in his learning for five years, will never experience it.

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^{1 Nili Fox, in Oxford Jewish Study Bible (1st ed.), p.302}