“And the princes of the congregation [counted] the sons of the Kehatites.” Why are the princes necessary here? Is it not so, that the Holy One blessed be He did not say to Moses that the princes of the congregation should be with him in the census of the Levites? Why did he do so?
Rather, this is what Moses said: ‘Since the princes were with me in the census of all Israel, just as it says: “And with you shall be [a man for each tribe, each is the head of his patrilineal house]” (Numbers 1:4), I will not cause them anguish and I will take them with me for the census of the Levites.’ From where is it derived that this is so? You find that after the census of Israel it is written: “These are the counted, that [Moses and Aaron, and the princes of Israel] counted” (Numbers 1:44), but after the census of the Levites, you do not find that the princes are mentioned there, but rather, “whom Moses and Aaron counted” (Numbers 4:37).
It is to teach you that the princes of Israel did not count the Levites at the directive of divine speech. But rather Moses took them with him in order to accord them honor.