Tehillim 133

1Hinei, mah tov umah na'im shevet achim gahm yachad (how good and how pleasant it is for brethren to dwell together in unity)! 2It is like the precious shemen upon the rosh, that ran down upon the beard, even Aharon's beard; that went down to the collar of his robes; 3As the tal of Chermon, and as the dew that descended upon the mountains of Tziyon; for there Hashem commanded the berakhah, even Chayyim Ad Olam.