20 Secondly, in the expression, “Mountain of God, Mountain full of curds,” Mountain “fruitful,” let no one dare from this to compare the Lord Jesus Christ with the rest of the Saints, who are themselves also called mountains of God....For there were not wanting men to call Him, some John Baptist, some Elias, some Jeremias, or one of the Prophets; He turns to them and says, “Why do ye imagine mountains full of curds, a mountain,” he says, “wherein it has pleased God to dwell therein”?.
“Why do ye imagine?” For as they are a light, because to themselves also has been said, “You are the Light of the world,” but something different has been called “the true Light which enlightens every man,” so they are mountains; but far different is the Mountain “prepared on the top of the mountains.” These mountains therefore in bearing that Mountain are glorious: one of which mountains says, “but from me far be it to glory, save in the Cross of our Lord Jesus Christ, through whom to me the world has been crucified, and I to the world:” so that “he has glories, not in himself, but in the Lord may glory.” “Why” then “do ye imagine mountains full of curds,” that “Mountain wherein it has pleased God to dwell therein”?
Not because in other men He dwells not, but because in them through Him. “For in Him dwells all the fullness of the Godhead,” not in a shadow, as in the temple made by king Solomon, but “bodily,” that is, solidly and truly....“For there is One God, and One Mediator of God and men, the Man Christ Jesus,” Mountain of mountains, as Saint of saints. Whence He says, “I in them and You in Me.” “Why then do ye imagine mountains full of curds, the mountain wherein it has pleased God to dwell in Him?” For those mountains full of curds that Mountain the Lord shall inhabit even unto the end, that something they may be to whom He says, “for without Me nothing you are able to do.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)