David penned this, and it is relevant to all periods of the church’s history and future.
There are two similitudes used to express the importance, necessity and loveliness of unity. Under the Old Testament, the anointing oil was a special compound not to be used for any other purpose. It signified the Holy Spirit, and the High Priest typifies Christ, who was anointed with the oil of gladness above His fellows. The Spirit and priestly ministry flow to all the members of His mystical body. Likewise, the dew speaks of the distillation of the Spirit in silent and soft descent, and also of the bedewment of the church by His holy doctrine.
We are not enjoined by Scripture to create unity, but Paul tells the Ephesians, “Endeavour to keep the unity of the Spirit.” It already exists, and the brethren must carefully and lovingly maintain and preserve it.
1 Behold, how good a thing it is,