What is the explanation of Psalm 133?

Behold, how good and how pleasant it is for brothers to dwell together in unity! It is like the precious oil upon the head, coming down upon the beard, even Aaron's beard, Coming down upon the edge of his robes. (NASB) Ps. 133:1-2

The precious oil is being used as an illustration of "brothers dwelling together in unity." Most of us will ask how does that make sense? The answer is found in Exodus 30:22-33.


Answer:

A Song of Ascents; of David.
Behold, how good and how pleasant it is for brothers to dwell together in unity.
Like precious oil anointed upon one's head, coming down upon the beard; Aaron's beard, which extends down upon the collar of his garments.
Like the dew of Mount Hermon, which flows down upon the mountains of Zion; for there God commanded the blessing of life for ever.