John Calvin Commentary Numbers 27:5

"And Moses brought their cause before Jehovah." — Numbers 27:5 (ASV)

And Moses brought their cause before the Lord. It is probable either that there was a difference of opinion, or that the minds of the judges were in doubt, concerning an obscure and uncertain point. At any rate, it was fitting that the law should be laid down by God, so that no future controversy would arise; for, if a sentence had been pronounced by human judgment on the matter before them, the obstinacy of many might not have been sufficiently settled.

It is worth noting the pious modesty of Moses, who was not ashamed to confess his ignorance until he had been instructed by the mouth of God. Although he had promulgated the law forty years before, still he was always ready to learn. Besides, there is no doubt that God impelled him to inquire of Him whenever any serious matters were in question, until his doctrine was absolutely perfect.

And, although God does not now deliver from heaven what should be done, nevertheless rulers are reminded that they should turn to God in perplexing situations, so that He may instruct them by the Spirit of wisdom; and assuredly they will not lack this, if they ask Him; since He is no less ready to listen to them than He showed Himself to be to Moses here.