Psalm 133 is very often quoted or sung in presbytery and general assembly meetings in the PCA and OPC. Rightfully so. It makes unity look very attractive indeed. However, whether the psalm is always rightly understood (in terms of how this unity comes about) may be doubted.
Two images serve to make unity attractive. The proprietary anointing oil coming down on Aaron’s beard, and the dew of Mount Hermon coming down to Zion (quite a ways from Mount Hermon, incidentally!) have one thing in common: both the oil and the dew come down, a fact noted by several commentators. It is not too much of a stretch to see a sort of geographical irony here, in that a psalm of ascent has something coming down.
More theologically, however, something coming down in this manner, particularly the dew of Mount Hermon, points to God’s grace. This unity is not so much an achievement, as it is a gift (see Kidner’s commentary, 134). All too often, unity is preached as law, not as gospel, as something which we achieve with little or no reference to God’s grace at all. Even when we pray for unity, our thoughts often run more along the lines of God’s simple enabling, rather than God’s grace actually accomplishing the unity.
The unity in question is a powerful one. If the dew of Mount Hermon (which is located in the far north of Israel) has repercussions for Zion, in the south, the implications have to do with the north-south tension already in evidence in David’s day. If this is a psalm of David, then the north-south tensions were already a matter for prayer. All the more so later on, when the two kingdoms split, but people still sang this psalm when they went up to Jerusalem for the feasts.
In Christ’s person and work, the potential for a unifying truth in the gospel has become a reality. Paul takes the widest sociological gaps he can think of (race, class, and sex) and claims that the gospel of Jesus Christ transcends those natural barriers. Notice something important about Paul’s claim. It is a unity built on the truth of the gospel, not a unity for unity’s own sake. The latter would be something that has no foundation and is inherently unstable. Contrary to the CWAGA folks (“Can’t We All Get Along?”), the prophets say, “How can two walk together unless they are agreed?” (Amos 3:3). Truth unifies. It does not divide. Modern Christianity needs to be reminded of this simple fact. Perhaps more unity could actually be achieved if these things could be remembered. Then we would pray for God to do it, to change our hearts towards the truth and towards those with whom we disagree. We need to pray for a unity based on truth.