The psalm was written by David during an occasion when he had enjoyed the harmony and peace of the family of God. Such occasions must have been oases in the desert for him, especially when he was being opposed by false friends and others. The psalm points to the privilege of being allowed access into such fellowship, the pleasantness of enjoying such fellowship, and the purpose of God that such fellowship should mark his people.
Adoption into God's family is the greatest privilege that a believer can have. Theoretically, a sinner could be justified (forgiven), sanctified (made holy) and glorified without being adopted. In addition to these blessings is the permanent status of adoption. One of the best things to do when feeling down in a spiritual sense is to read the various New Testament verses that describe various aspects of the fatherhood of God.
The psalmist likens this relationship to the oil with which the high priest was anointed and to the dew that descended on the mountains of Israel. The people had read the accounts of the anointing of their priest and would have experienced the refreshing dew on a daily basis.
Both the oil and the dew are symbols of the presence of the Holy Spirit with his people. The illustration of the oil indicates that the presence of the Spirit was connected to the intercession of the high priest. When he was anointed with oil, the oil flowed on to his shoulders and down his clothes. Jesus is our high priest and we know that on his inauguration, after he ascended to heaven, he was anointed with the Spirit. On the Day of Pentecost, the oil flowed down to the church in Jerusalem and it has been flowing from Jesus to his people ever since.
The illustration of dew on Mount Hermon and Mount Zion perhaps points to the great reality that all God’s people, the big and the small, possess this copious Spirit. Hermon was a large mountain whereas Zion was a small hill, yet both enjoyed the presence of the dew. No Christian can say that he does not possess the Holy Spirit. Whatever his spiritual gifts, experiences, and attainments, he has the Spirit of unity.
This Holy Spirit-given brotherly love has many benefits. Like the oil and the dew, it is refreshing, and it spreads. Clearly, unity of believers is very desirable. There are many ways by which unity can be presented. The Lord’s people should be one doctrinally, should be one practically, and should be one internally from the heart.