From Chabad.org: This Aliya describes the “test of the staffs.” G‑d tells Moses to take a staff from each of the twelve tribes, with the name of each tribe’s prince written upon their staff. Another staff was taken to represent the tribe of Levi, and Aaron’s name was written on that staff. These staffs were placed overnight in the Holy of Holies chamber of the Tabernacle. Next morning they were removed, and miraculously Aaron’s staff had budded with almond blossoms and almonds. This was further proof that Aaron was G‑d’s choice for High Priest.
Of all the random miracles, ripe almonds growing overnight on a stick with a tribal leader’s name on it is pretty high on the list. But since we know nothing in the Torah is random, ripe almonds must represent something more. Rashi helps by saying that almonds are the fastest growing “fruits”, and it represents the possibility of immediate reward/punishment by G-d. G-d could have chosen to sprout fruits that normally take longer, but instead left the Israelites with a message of warning for those that question Him, and a lasting message for those that adhere to His word.