Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
(Or ch.17:16-28). Confirmation of the High-Priesthood of Aaron. - Whilst the Lord had thus given a practical proof to the people, that Aaron was the high priest appointed by Him for His congregation, by allowing the high-priestly incense offered by Aaron to expiate His wrath, and by removing the plague; He also gave them a still further confirmation of His priesthood, by a miracle which was well adapted to put to silence all the murmuring of the congregation.
He commanded Moses to take twelve rods of the tribe-princes of Israel, one for the fathers' house of each of their tribes, and to write upon each the name of the tribe; but upon that of the tribe of Levi he was to write Aaron's name, because each rod was to stand for the head of their fathers' houses, i.e., for the existing head of the tribe; and in the case of Levi, the tribe-head was Aaron. As only twelve rods were taken for all the tribes of Israel, and Levi was included among them, Ephraim and Manasseh must have been reckoned as the one tribe of Joseph, as in Deu 27:12. These rods were to be laid by Moses in the tabernacle before the testimony, or ark of the covenant (Exo 25:21; Exo 29:42). And there the rod of the man whom Jehovah chose, i.e., entrusted with the priesthood (see Num 16:5), would put forth shoots, to quiet the murmuring of the people. שׁכך, Hiph., to cause to sink, to bring to rest, construed with מעל in a pregnant signification, to quiet in such a way that it will not rise again.
Moses carried out this command. And when he went into the tabernacle the following morning, behold Aaron's rod of the house of Levi had sprouted, and put forth shoots, and had borne blossoms and matured almonds. And Moses brought all the rods out of the sanctuary, and gave every man his own; the rest, as we may gather from the context, being all unchanged, so that the whole nation could satisfy itself that God had chosen Aaron. Thus was the word fulfilled which Moses had spoken at the commencement of the rebellion of the company of Korah (Num 16:5), and that in a way which could not fail to accredit him before the whole congregation as sent of God.
So far as the occurrence itself is concerned, there can hardly be any need to remark, that the natural interpretation which has lately been attempted by Ewald, viz., that Moses had laid several almond rods in the holy place, which had just been freshly cut off, that he might see the next day which of them would flower the best during the night, is directly at variance with the words of the text, and also with the fact, that a rod even freshly cut off, when laid in a dry place, would not bear ripe fruit in a single night. The miracle which God wrought here as the Creator of nature, was at the same time a significant symbol of the nature and meaning of the priesthood. The choice of the rods had also a bearing upon the object in question. A man's rod was the sign of his position as ruler in the house and congregation; with a prince the rod becomes a sceptre, the insignia of rule (Gen 49:10). As a severed branch, the rod could not put forth shoots and blossom in a natural way. But God could impart new vital powers even to the dry rod. And so Aaron had naturally no pre-eminence above the heads of the other tribes. But the priesthood was founded not upon natural qualifications and gifts, but upon the power of the Spirit, which God communicates according to the choice of His wisdom, and which He had imparted to Aaron through his consecration with holy anointing oil. It was this which the Lord intended to show to the people, by causing Aaron's rod to put forth branches, blossom, and fruit, through a miracle of His omnipotence; whereas the rods of the other heads of the tribes remained as barren as before. In this way, therefore, it was not without deep significance that Aaron's rod not only put forth shoots, by which the divine election might be recognised, but bore even blossom and ripe fruit. This showed that Aaron was not only qualified for his calling, but administered his office in the full power of the Spirit, and bore the fruit expected of him. The almond rod was especially adapted to exhibit this, as an almond-tree flowers and bears fruit the earliest of all the trees, and has received its name of שׁקד, "awake," from this very fact (cf. Jer 1:11).
God then commanded (Num 17:10, Num 17:11) that Aaron's rod should be taken back into the sanctuary, and preserved before the testimony, "for a sign for the rebellious, that thou puttest an end to their murmuring, and they die not." The preservation of the rod before the ark of the covenant, in the immediate presence of the Lord, was a pledge to Aaron of the continuance of his election, and the permanent duration of his priesthood; though we have no need to assume, that through a perpetual miracle the staff continued green and blossoming. In this way the staff became a sign to the rebellious, which could not fail to stop their murmuring.
This miracle awakened a salutary terror in all the people, so that they cried out to Moses in mortal anguish, "behold, we die, we perish, we all perish! Every one who comes near to the dwelling of Jehovah dies; are we all to die?" Even if this fear of death was no fruit of faith, it was fitted for all that to prevent any fresh outbreaks of rebellion on the part of the rejected generation.