Psalm 133 is a very short Psalm, consisting of only 3 verses. It shows us the joy of living in unity. One of the things that drives people away from the body of Christ is that the people of Christ don't live in unity: they don't love to be together nor do they serve one another joyfully. When you see people loving each other, it's the most irresistible thing on earth. God's church should be unified in its proclamation, purpose, passion, product, and praise.