Notice what David writes:
Psalms 133:1.... Behold, how good and how pleasant it is for brethren to dwell together in unity!
The word good has the meaning of "beneficial".
The word pleasant has the meaning of "beauty".
The word dwell has the meaning of "a relationship as in marriage".
David recording words for eternity writes of the benefit, the beauty, and the relationship found only in unity of the believers. Just think... if David is this excited in seeing God's people in unity think how this must please our Lord.
May we all, as believers, strive to dwell together in unity.