A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
num 17:2AARON'S ROD FLOURISHES. (Num 17:1-13)
Speak unto the children of Israel--The controversy with Moses and Aaron about the priesthood was of such a nature and magnitude as required a decisive and authoritative settlement. For the removal of all doubts and the silencing of all murmuring in the future regarding the holder of the office, a miracle was wrought of a remarkable character and permanent duration; and in the manner of performing it, all the people were made to have a direct and special interest.
take of every one . . . princes . . . twelve rods--As the princes, being the oldest sons of the chief family, and heads of their tribes, might have advanced the best claims to the priesthood, if that sacred dignity was to be shared among all the tribes, they were therefore selected, and being twelve in number--that of Joseph being counted only one--Moses was ordered to see that the name of each was inscribed--a practice borrowed from the Egyptians--upon his rod or wand of office. The name of Aaron rather than of Levi was used, as the latter name would have opened a door of controversy among the Levites; and as there was to be one rod only for the head of each tribe, the express appointment of a rod for Aaron determined him to be the head of that tribe, as well as that branch or family of the tribe to which the priestly dignity should belong. These rods were to be laid in the tabernacle close to the ark (compare Num 17:10 and Heb 9:4), where a divine token was promised that would for all time terminate the dispute.
num 17:6the rod of Aaron was among their rods--either one of the twelve, or, as many suppose, a thirteenth in the midst (Heb 9:4). The rods were of dry sticks or wands, probably old, as transmitted from one head of the family to a succeeding.
num 17:8Moses went into the tabernacle--being privileged to do so on this occasion by the special command of God. And he there beheld the remarkable spectacle of Aaron's rod--which, according to JOSEPHUS, was a stick of an almond tree, bearing fruit in three different stages at once--buds, blossoms, and fruit.
num 17:10Bring Aaron's rod again before the testimony, to be kept for a token against the rebels--For if, after all admonitions and judgments, seconded by miracles, the people should still rebel, they would certainly pay the penalty by death.
num 17:12Behold, we die, we perish--an exclamation of fear, both from the remembrance of former judgments, and the apprehension of future relapses into murmuring.
num 17:13cometh any thing near--that is, nearer than he ought to do; an error into which many may fall. Will the stern justice of God overtake every slight offense? We shall all be destroyed. Some, however, regard this exclamation as the symptom or a new discontent, rather than the indication of a reverential and submissive spirit. Let us fear and sin not.