This psalm is one of the last Songs of Ascents; this one has the theme of "unity". It begins by DECLARING THE CONDITION of unity among believers ("good" = beautiful, a condition describing benefit; "pleasant"= harmony, a musical term calling to mind the aspect of how wonderful music can be when instruments play together; a condition describing agreement, concord.) When believers are unified, there are benefits and happiness. When believers are unified, it is only achieved when they are in sync, when they understand the necessity of and the function of harmonious operations. Brothers (relational) together (positional) in unity (conditional) That is our FOCUS.
To complete the understanding of unity, David uses pictures ("like") for DECLARING THE FEATURES of unity. 1. Like the oil anointing the head of the priest > abundant, fragrant, a testimony to his position and his purpose; reminder of God's presence. 2. Like the dew of Hermon (the highest mountain; constantly blessed with refreshment which it freely shares with the mountains below it [Zion]) > refreshing, contributing to fruitfulness, providing life.
So what? How unified are you in/to the community of faith? Are you a benefit to your brothers and sisters in Christ -- or a liability/problem? How obvious is your testimony of your faith in Christ? Are you a believer? If not, why not? If so, how so? Is your spiritual life abundant and obvious? Are others aware of your faith and encouraged by your faith in Jesus? How refreshing is it to others in the body? Is it a contribution to the fruitfulness of others in the Body? Does your life in Christ provide REAL LIFE to others - both to those who know Him, and to those who don't?