Matthew Henry on Numbers 17:1-7

It is an instance of the grace of God, that, having wrought divers miracles to punish sin, he would work one more to prevent it. Twelve rods or staves were to be brought in. It is probable that they were the staves which the princes used as ensigns of their authority; old dry staves, that had no sap in them. They were to expect that the rod of the tribe, or prince, whom God chose to the priesthood, should bud and blossom. Moses did not object that the matter was sufficiently settled already; he did not undertake to determine it; but left the case before the Lord.