Tafsiran Bilangan 17:23: Rashi, Kli Yakar, Or HaChaim & Rashbam

ויצא פרח AND IT BROUGHT FORTH A BLOSSOM — Take this as what it literally implies.

“And behold, Aaron’s rod blossomed, etc.” This hints that God does not judge by what appears to human eyes. Even if one appears as a dry stick without the moisture of water, Torah, and wisdom, the Holy One, Blessed be He, can make it blossom. And conversely, as concluded in the Yalkut (in Ezekiel 17, see there) which interpreted regarding Korah and Aaron the verse I have dried up the green tree and made the dry tree flourish (Ezekiel 17:24).
It may be that from here extends the source that everything in the Temple was blooming and bearing fruit, even the gold that was called parvaim [choice gold]. And it brought forth blossoms — this was a sign for the young priests who were called pirchei kehunah [the flowers of priesthood]. And it budded [yatzetz tzitz] — this is a sign for the high priests who wore the tzitz, the holy crown. And it yielded almonds — this was in the merit of he ran into the midst of the congregation, etc. to stop the plague, and in the merit that priests are zealous in their service, God rewarded him by yielding almonds, which connotes diligence [shekidut] and swiftness. And he merited the gifts, as it is said, And I, behold, I have given you (Numbers 18:8).
The language of “behold” [hineh] indicates zealousness, as Rashi explained in Parashat Vayeshev (Genesis 37:13) on And he said, “Here I am” [hineni] — an expression of humility and zealousness. And Rashi explained here that “behold” [hineh] indicates joy, as it says, Behold, he is coming out to meet you, and when he sees you, he will be glad in his heart (Exodus 4:14).
The reason for this is that every “hineh” [behold] is an expression of zealousness, and whenever a person acts zealously, surely they are happy in their actions. Just as Aaron was happy to greet his brother Moses, who was younger than him, and was not jealous of his authority, in this merit Aaron was given the authority of the priesthood to be anointed with joy. This is what is meant by And I, behold, I have given you — in the merit of behold, he is coming out to meet you.
And above in the verse in the morning, the Lord will make known, God gave him the gifts in the morning with a shining face, with joy, as is customary for everything given properly to one who asks. And our Sages said (Shabbat 139a) that in the merit of and when he sees you, he will be glad in his heart, Aaron deserved to wear the breastplate of judgment on his heart, because it is said He guides the humble in justice (Psalms 25:9). As was explained above in Parashat Mishpatim (Exodus 21:1), this path of humility was his, that he rejoiced in his brother’s authority.
And our Sages said (Chullin 89a): Great is what was said about Moses and Aaron, as it is written What are we? (Exodus 16:8). And likewise concerning Aaron it is written And what is Aaron? (Numbers 16:12). For he considered himself as nothing, as if he were a dry stick with no moisture at all. Therefore, he merited that Aaron’s dry rod blossomed.

ויגמל שקדים, it bore ripe almonds. Our sages in Bamidbar Rabbah 18,23 say that the reason G'd chose almonds was to serve as a warning that anyone who would challenge that the priesthood belonged to the descendants of Aaron would be dealt with very promptly. It appears to me that what forced the sages to come to this conclusion was that if someone is desirous of having a miracle performed for him he does not wish the fruit to ripen prematurely as this could reflect something negative about the one who performs the miracle and is unable to deliver fully ripened fruit. If G'd nonetheless exposed Himself to such an interpretation by the people who watched this miracle it could only be because He had considerations which outweighed those of how His own image was being perceived.

ציץ is the first stage in the growth of the fruit when the blossom has fallen off.