@Ps 133:1-3. The blessings of fraternal unity.
1, 2. As the fragrant oil is refreshing, so this affords delight. The holy anointing oil for the high priest was olive oil mixed with four of the best spices (@Ex 30:22,25,30). Its rich profusion typified the abundance of the Spirit's graces. As the copious dew, such as fell on Hermon, falls in fertilizing power on the mountains of Zion, so this unity is fruitful in good works.
3. there--that is, in Zion, the Church; the material Zion, blessed with
enriching dews, suggests this allusion the source of the influence
enjoyed by the spiritual Zion.
commanded the blessing--(Compare @Ps 68:28).