Unity (Dictionary): The fact quality or condition of being one; oneness; singleness; a union of parts forming a complex whole.
Unity (Bible): Unitedness; one; oneness; that which binds together.
Psalm 133: 1Behold, how good and how pleasant it is for brethren to dwell together in unity! 2It is like the precious ointment poured on the head, that ran down on the beard, even the beard of Aaron [the first high priest], that came down upon the collar and skirts of his garments [consecrating the whole body]. 3It is like the dew of [lofty] Mount Hermon and the dew that comes on the hills of Zion; for there the Lord has commanded the blessing, even life forevermore [upon the high and the lowly]. (AMP)
As we read this passage written by David we can see his heart and his deep understanding of fellowship and unity. The word “unity” used here literally means “to live life together”. If we go back to Exodus 29 we see how God wanted his priesthood to be anointed for service:
Exodus 29: 4-7: 4And bring Aaron and his sons to the door of the Tent of Meeting [out where the laver is] and wash them with water.5Then take the garments and put on Aaron the long and sleeved tunic and the robe of the ephod and the ephod and the breastplate, and gird him with the skillfully woven girding band of the ephod. 6And you shall put the turban or miter upon his head and put the holy crown upon the turban. 7Then take the anointing oil and pour it on his head and anoint him. (AMP)
The oil was symbolic of the Holy Spirit anointing and was reserved for the prophets, priests and kings. But we know today that the children of God are all anointed by the Holy Spirit and are considered priests:
1 Peter 2:9: 9-10But you are the ones chosen by God, chosen for the high calling of priestly work, chosen to be a holy people, God’s instruments to do his work and speak out for him, to tell others of the night-and-day difference he made for you—from nothing to something, from rejected to accepted. (Message)
God has taken us from being lost to being part of a royal priesthood in service to Him! He has taken us out of the miry clay, cleaned us and set us on a rock (Jesus) (Psalm 40: 1-3). His priests must be clean! The blood of Jesus makes us clean and the water baptism is our witness of His hand on us. God has always wanted His children to be one with each other. Jesus has made that possible!