Albert Barnes Commentary Numbers 17:8

"And it came to pass on the morrow, that Moses went into the tent of the testimony; and, behold, the rod of Aaron for the house of Levi was budded, and put forth buds, and produced blossoms, and bare ripe almonds." — Numbers 17:8 (ASV)

Yielded almonds – “Ripened almonds,” that is, “brought forth ripe almonds.” The name almond in Hebrew denotes the “waking-tree” and the “waking-fruit”; and it is applied to this tree because it blossoms early in the season. It serves here, as in Jeremiah 1:11-12, to set forth the speed and certainty with which, at God’s will, His purposes are accomplished.

So again, the blossoming and bearing of Aaron’s rod—naturally impotent when severed from the parent tree—may signify the profitableness (due to God’s appointment and blessing) of the various means of grace (for example, the priesthood, the sacraments). For these means, of themselves and apart from Him, could have no such efficacy. Compare Isaiah 4:2; Isaiah 11:1; Isaiah 53:2; Jeremiah 33:5; Zechariah 6:12.