In this Torah portion, Korach conspires to rebel against Moses and Aaron, and his conspiracy fails, and he is destroyed along with his conspirators. Keen to show the tribes of Israel that the Tribe of Levi has religious authority over the other tribes, God tells Moses to ask the heads of the tribes to take their rods (מַּטֹּת, or matot) and engrave their names on them (or some say the names of their tribes). Interestingly, Matot will be the name of a future Torah portion in Numbers. Just as the English word staff has a double meaning of both a rod, and a group of employees, so in Hebrew, matot can also refer to a group of subordinates as well as a wooden staff.
God told Moses to gather the rods, along with Aaron's rod, and to place them inside the Tabernacle, before the Ark. Recall that in Exodus, Aaron demonstrated before the priests of Egypt that he could cast his rod on the ground, and have it turn into a serpent. This is the same rod. God tells Moses that the rod of the man whom God would choose would blossom inside the Tabernacle, and by this God would choose the proper leader of the tribes.
The next day, Moses went to get the rods from inside the tent. Aaron's rod had sprouted leaves, and now blossoms and almonds were ripening upon it. The leaders of the other tribes were terrified by this demonstration, and God told Moses to put Aaron's rod before the Ark as a testament that Aaron's authority came from Divine right.
The symbol of the almond appears elsewhere in the Bible, and in Freemasonry as well. In Ecclesiastes 12:5, the candidate is told that "Also when they shall be afraid of that which is high, and fears shall be in the way, and the almond tree shall flourish, and the grasshopper shall be a burden, and desire shall fail: because man goeth to his long home, and the mourners go about the streets." The almond tree shall flourish because its blossoms are white, and so a metaphor for old age, as white hair growing on the head of an older person.
Of course, Aaron's rod is familiar to every Royal Arch Mason as well, for reasons improper to divulge.