Among the ancients the key was a symbol of authority and power; this was true among the Hebrews. Following this ancient symbolism the crossed keys are the Jewel of the Treasurer of a Lodge, because he is responsible for the purse and for receiving and paying out the funds for the Fraternity. In the Royal Arch Degree and in the Secret Master, or Fourth Degree of the Scottish Rite, the key is the symbol of secrecy. It is a reminder that the secrets of Freemasonry are to be locked up or concealed in the heart. — ( Isaiah 22:22 - Matthew 16:19 )
Biblical Reference
Isaiah 22:22
And the key of the house of David will I lay upon his shoulder; so he shall open, and none shall shut; and he shall shut, and none shall open.
Matthew 16:19
And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.
~~ooOoo~~
This page is adapted from the Glossary at Phoenixmasonry — Used with permission.