6 But love such mountains, in whom the Lord is. Then do those very mountains love you, if you have not placed hope in them. See, brethren, what the mountains of God are. Thence they are so called in another passage: “Your righteousness is like the mountains of God.” Not their righteousness, but “Your righteousness.” Hear that great mountain the Apostle. “That I may be found in Him, not having my own righteousness, which is of the law, but that which is through the faith of Christ.” But they who have chosen to be mountains through their own righteousness, as certain Jews or Pharisees their rulers, are thus blamed: “Being ignorant of God's righteousness, and going about to establish their own righteousness, they have not submitted themselves unto the righteousness of God.” But they who have submitted themselves are exalted in such a manner as to be humble.
In that they are great, they are mountains; in that they submit themselves unto God, they are valleys: and in that they have the capacity of piety, they receive the plenteousness of peace, and transmit the copious irrigation to the hills, only beware, at present, what mountains you love. If you wish to be loved by good mountains, place not your trust even in good mountains. For how great a mountain was Paul? Where is one like him found? We speak of the greatness of men. Can any one readily be found of so great grace?
Nevertheless, he feared lest that bird should place trust in him: and what does he say: “Was Paul crucified for you?” But lift up your eyes unto the mountains, whence help may come unto you: for, “I have planted, Apollos has watered:” but, your help comes from the Lord, who has made Heaven and earth; for, “God gave the increase.” “The mountains,” therefore, “stand around Jerusalem.” But as “the mountains stand around Jerusalem, even so stands the Lord round about His people, from this time forth for evermore.”
If therefore the mountains stand around Jerusalem, and the Lord stands round about His people, the Lord binds His people into one bond of love and peace, so that they who trust in the Lord, like the mount Sion, may not be moved for evermore: and this is, “from this time forth for evermore.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)