The theme of descending continues from the previous verse. The dew descends from Mount Hermon upon the mountains of Zion. Hermon, in the Ante-Lebanon range, is the highest point in the north of Palestine. Zion, in Judea, is far to the south. As in verse 2, in which the oil runs from the top of Aaron's head all the way down to the hem of his skirt, this is another "top to bottom" image. If we imagine Palestine aso a body, Hermon is at the "head," and the dew flows all the way down to Zion near the "feet," covering the whole land.
The word Hermon means "devoted" or "sanctified"—holy. It was another holy mountain, and it looks like one too. Its 9,000-feet-high peak is perpetually snowcapped and can be seen from miles away. It is a majestic mountain, picture-postcard perfect, a fitting place to represent God. (As an aside, some scholars think Hermon is the mount where Christ was transfigured, where He revealed His glory to His disciples.)
There is another good reason why David chose Hermon as the place from which the water descended down into Zion. Zion, of course, is a pointed, symbolic reference to the church of God. In Zion, members of the church are all brethren, and this dew, a metaphor for unity, symbolic of the Holy Spirit, descends down to us from the majestic heights of the holy mountain, representing the Head, Jesus Christ.
Richard T. Ritenbaugh