The vessels on the side of the Ark were placed there as testimony for future generations. Aaron's staff that blossomed with buds and flowers following the controversy regarding Korach and his followers was testimony that the Almighty had chosen the descendants of Aaron for the priesthood, for all time. The jar which held some Manna from the time of the desert, was testimony to the continuous protection which the Almighty provides to the Nation of Israel. The jar which held the anointing oil made by Moses, was used to anoint kings and High Priests. 
The Anointing Oil
Contents:   Part I,    Part II,    Part III,    Part IV,    Part V,    Part VI,    Part VII