The psalm opens with an exclamation: behold, how good and pleasant it is when brothers dwell in unity! The word brothers can refer to a family or to the whole people of Israel, who gathered in Jerusalem. The psalm does not describe a distant ideal but an experience that can be seen and tasted.
Verse 2 offers the first picture: it is like the precious oil on the head, running down on the beard, on the beard of Aaron, running down on the collar of his robes. It was the anointing oil of the high priest, which consecrated Aaron to serve God. It is abundant, fragrant and consecrated: unity flows over everyone, from head to hem.
Verse 3 adds the second picture: it is like the dew of Hermon, which falls on the mountains of Zion. Hermon is a high mountain in the north, covered with snow, whose abundant dew refreshes the land. And it ends with the reason for it all: there the Lord has commanded the blessing, life forevermore.