Numbers 17:9
And Moses brought out all the rods from before the LORD unto all the children of Israel: and they looked, and took every man his rod. And Moses brought out all the rods from before the LORD unto all the children of Israel: and they looked, and took every man his rod.
Moses brought all the rods out from before the LORD to all the children of Israel, and they looked them over and each man recognized and took his own rod. Aaron's rod stood visibly apart from all the rest, for in a single night it had miraculously budded and blossomed and yielded ripe almonds. That public display proved that God had chosen Aaron's house, the family of Levi, for the priesthood.
By that open contrast the dispute over who should serve in the priesthood was settled, the people's complaints were silenced, and their minds were set at rest after the rebellion. The rod was then kept as a lasting reminder of God's decision and as a warning against renewed rebellion and murmuring.