Psalm 133 states in the King James Version, which is in the public domain:
1 A Song of degrees of David. Behold, how good and how pleasant it is for brethren to dwell together in unity!
2 It is like the precious ointment upon the head, that ran down upon the beard, even Aaron’s beard: that went down to the skirts of his garments;
3 As the dew of Hermon, and as the dew that descended upon the mountains of Zion: for there the LORD commanded the blessing, even life for evermore.
There are a variety of ideas about the historical reference-point for this Psalm. Some relate it to II Samuel 19:9, 14, in which all of Israel united in asking David to return and re-assume the throne (after David had fled due to Absalom’s revolt). Others apply it to Hezekiah’s Passover festival in II Chronicles 30, which drew some pilgrims from Northern Israel. V 3 mentions Hermon, after all, and that was in the north. A third view is that the part about Aaron was added later, and the Psalm originally was just about the beauty of unity among brothers. W.O.E. Oesterley argues that it concerns Israelite family life, such as brothers living together, and the institution of levirate marriage (in which a man marries his brother’s wife when the brother dies, in order to raise up offspring for the deceased brother). I’m somewhat drawn to the second interpretation, the one about Hezekiah’s passover. According to II Chronicles 30, Northern Israelites came to Jerusalem from the north (v 3), Northern and Southern Israelites were united during that festival, and the festival was at Jerusalem, the site of the Aaronic priesthood (v 2), which brought blessing to Israel.
Unity. The concept gives me the heeby-jeebies, since it sounds to me like uniformity: everyone believing the same way and having the same mission. But I’m more comfortable with the notion that people should be united in love: united in the acceptance of love as an important way of life, and in the practice of love.