All of these expressions are natural in view of the significance of the rod. It was called the “rod of God,” for it was the symbol of His authority; it was Moses’ rod, because it belonged to him and was carried by him; it was also Aaron’s rod, because Aaron at times spoke and acted for Moses. It is to be noted, however, that these “rod passages” because of the variety of expression found in them, have been used to support the widely held Documentary Hypothesis. Exodus 4:24; 7:15, 17; 9:23; 10:13; 14:16; 21:20 are split in two and divided in the main between documents J and E. This is a striking example of the extremes to which the advocates of this theory are obliged to go in order to work out their analysis. Yet the variety of expression is in entire harmony with the situation as it is represented in the Biblical narrative.
S. R. Driver, Introduction to the Literature of the Old Testament (1910), 20-30; E. S. Brightman, The Sources of the Hexateuch (1918), 82, et passim.
International Standard Bible Encyclopedia (1915)
Immediately after the incidents connected with the rebellion of Korah, Dathan and Abiram against the leadership of Moses and the priestly primacy of Aaron (Nu 16), it became necessary to indicate and emphasize the Divine appointment of Aaron. Therefore, at the command of Yahweh, Moses directs that twelve almond rods, one for each tribe with the prince’s name engraved thereon, be placed within the Tent of the Testimony. When Moses entered the tent the following day, he found that Aaron’s rod had budded, blossomed and borne fruit, "the three stages of vegetable life being thus simultaneously visible." When the miraculous sign was seen by the people, they accepted it as final; nor was there ever again any question of Aaron’s priestly right. The rod was kept "before the testimony" in the sanctuary ever after as a token of the Divine will (Nu 17:10). The writer of Hebrews, probably following a later Jewish tradition, mentions the rod as kept in the Holy of Holies within the ark (He 9:4; compare 1Ki 8:9). See Priest, III.