8 But ye should know what Hermon is. It is a mountain far distant from Jerusalem, that is, from Sion. And so it is strange that he says thus: As the dew of Hermon, which fell upon the mountains of Sion, since mount Hermon is far distant from Jerusalem, for it is said to be over Jordan. Let us then seek out some interpretation of Hermon. The word is Hebrew, and we learn its meaning from them who know that language. Hermon is said to mean, a light set on a high place. For from Christ comes the dew. No light is set on a high place, save Christ. How is He set on high? First on the cross, afterwards in heaven. Set on high on the cross when He was humbled; humbled, but His humiliation could not but be high. The ministry of man grew less and less, as was signified in John; the ministry of God in our Lord Jesus Christ increased, as was shown at their birth. The former was born, as the tradition of the Church shows, on the 24th of June, when the days begin to shorten. The Lord was born on the 25th of December, when the days begin to lengthen. Here John himself confessing, “He must increase, but I must decrease.” And the passion of each shows this. The Lord was exalted on the cross; John was diminished by beheading. Thus the light set on high is Christ, whence is the dew of Hermon....But if he have the dew of Hermon, which fell on the hill of Sion, he is quiet, peaceable, humble, submissive, pouring forth prayer in place of murmuring. For murmurers are admirably described in a certain passage of the Scriptures, “The heart of a fool is as the wheel of a cart.” What is the meaning of “the heart of a fool is as the wheel of a cart”? It carries hay, and creaks. The wheel of a cart cannot cease from creaking. Thus there are many brethren, who do not dwell together, save in the body. But who are they who dwell together? They of whom it is said, “And they had one mind and one heart towards God.”
9. “Because there the Lord commanded blessing.” Where did He command it? Among the brethren who dwell together. There He enjoined blessing, there they who dwell with one heart bless God. For you bless not God in division of heart....Are you straitened on earth? Depart, have your habitation in heaven. How shall I, a man clothed in flesh, enslaved to the flesh, you will say, have my habitation in heaven. First go in heart, whither you would follow in the body. Do not hear, “Lift up your hearts,” with a deaf ear. Keep your heart lifted up, and no one will straiten you in heaven.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)