Psalms 133:3

As the dew of Hermon, and as the dew that descended upon the mountains of Zion. From the loftier mountains the moisture appears to be wafted to the lesser hills: the dews of Hermon fall on Zion. The Alpine Lebanon ministers to the minor elevation of the city of David; and so does brotherly love descend from the higher to the lower, refreshing and enlivening in its course. Holy concord is as dew, mysteriously blessed, full of life and growth for all plants of grace. It brings with it so much benediction that it is as no common dew, but As that of Hermon which is specially copious, and far reaching. The proper rendering is, "As the dew of Hermon that descended upon the mountains of Zion", and this tallies with the figure which has been already used; and sets forth by a second simile the sweet descending diffusiveness of brotherly unity. For there the Lord commanded the blessing, even life for evermore. That is, in Zion, or better still, in the place where brotherly love abounds. Where love reigns God reigns. Where love wishes blessing, there God commands the blessing. God has but to command, and it is done. He is so pleased to see his dear children happy in one another that he fails not to make them happy in himself. He gives especially his best blessing of eternal life, for love is life; dwelling together in love we have begun the enjoyments of eternity, and these shall not be taken from us. Let us love for evermore, and we shall live for evermore. This makes Christian brotherhood so good and pleasant; it has Jehovah's blessing resting upon it, and it cannot be otherwise than sacred like "the precious ointment", and heavenly like "the dew of Hermon." O for more of this rare virtue!

As the dew of Hermon, and as the dew that descended upon the mountains of Zion - This was not Mount Zion, ציון tsiyon, in Jerusalem, but Sion, שיאן which is a part of Hermon, see Deu 4:48: “Mount Sion, which is Hermon.” On this mountain the dew is very copious. Mr. Maundrell says that “with this dew, even in dry weather, their tents were as wet as if it had rained the whole night.” This seems to show the strength of the comparison. For there - Where this unity is. The Lord commanded the blessing - That is, an everlasting life. There he pours out his blessings, and gives a long and happy life. For other particulars, see the commentators passim, and the following analysis.

As the dew of Hermon ... - On the situation of Mount Hermon, see the notes at Psa 89:12. The literal rendering of this passage would be, “Like the dew of Hermon which descends on the mountains of Zion.” According to our version two things are referred to: the dew of Hermon, and the dew on the mountains of Zion, But this is not in the original. There no dew is referred to but that which belongs to Hermon. It has, of course, been made a question how the dew of Hermon, a remote mountain, could be said to descend on the mountains of Zion, and our translators have sought to solve the difficulty by inserting the words “and as the dew.” Some have supposed that the proper interpretation is to refer the comparison in the passage to the dew of Hermon, and that all which follows is an application of the thought: “Like the dew of Hermon is the influence which comes down upon the mountains of Zion,” etc. The most probable and plausible interpretation, however, it seems to me, is, that the mind of the poet was turned to the dew of Hermon - to the gentleness, and the copiousness, and the vivifying nature of that dew - diffusing beauty and abundance all around - and that he thought of that dew, or dew like that, as descending on the mountains of Zion. Not that the dew of Hermon actually descended there; but when changing the comparison, in illustration of brotherly love, from oil to dew, he most naturally thought (perhaps from some former observation) of the dew of Hermon, and immediately thought of Zion as if that dew descended there: that is, love, unity, and concord there would be as if the dew of Hermon should descend on the barren hills of Zion or Jerusalem, there diffusing beauty, abundance, fertility. The comparison of the influence of brotherly love, or unity, with dew is not a forced or unnatural one. […]

I've learned that broken covenants impact your spiritual authority because disunity diminishes the anointing (Ps. 133) and creates conditions for the curse.