«Aaron's rod»; matteh[maṭēh] מטה [Heb.] ;
ῥάβδος [ραβδος] (Septuagint) [Gk]; virga [L.];

A rod that was transformed into a serpent before the Pharaoh, and it budded and bloomed revealing Aaron to be the one chosen to lead (be High Priest).

§ Exodus

In Egypt, when the Pharaoh demanded Moses to demonstrate a marvel, he made his brother Aaron's rod turn into serpent^*1.

This episode is well-known, but it is probably worth noting that in the orignal text, the rod was transformed into a tanin תנין "dragon" [Heb.], a word that has been employed in modern Hebrew to mean "crocodile". In the Septuagint, it is a drakon δράκων, and the Vulgate has coluber "serpent".

That is to say, the creature is different (or is designated by a different word) from the "serpent" nahash נחש of the Garden of Eden^*2.
The distinction maintained by the seventy translators of the Septuagint (who called it ophis ὄφις "snake") and by St. Jerome (serpens).

Pharaoh's wizards were also able to transform their rods to tanin, but Aaron' rod gobbled up the rods of the other wizards.

Subsequently, the Hebrew God causes The Nine Plagues. The waters of Egypt turn to blood when either Moses or Aaron struck the water of the Nile with his rod. The plague of frogs and flies(gnats) is invoked by Aaron's rod. Moses by lifting his hands causes the plague of locusts to devour the crops, and when he raises his rod it brings forth the east wind that carries the locusts to Egypt.

Hence there arises speculation that the rod of the two men are one and the same -- this is expounded upon in the Jewish commentaries (Midrash haggadah)^*3 which makes the rod an heirloom treasure throughout the ages.

§ Budding Rod

Later, when unbelievers challenged the faith, Moses had Aaron's rod (inscribed with the name of the house of Levi) laid in front of the Ark of the Covenant, alongside the representive rods of other tribes, in a test to see who would be revealed as the chosen one. By the next day, Aaron's rod budded and almond blossoms bloomed.^*1 Thereafter the rod was kept in the Ark as testament to those who might disbelieve.