As the mountains are round about Jerusalem, so the LORD is round about his people from this time forth even forever.
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Augustine of Hippo
3. Who are these? "They shall stand fast for ever, who dwell in Jerusalem" (ver. 2). If we understand this earthly Jerusalem, all who dwelt therein have been excluded by wars and by the destruction of the city: thou now seekest a Jew in the city of Jerusalem, and findest him not. Why then will "they that dwell in Jerusalem not be moved for ever," save because there is another Jerusalem, of which ye are wont to hear much? She is our mother, for whom we sigh and groan in this pilgrimage, that we may return unto her. ...They then who dwell therein "shall never be moved." But they who dwelt in that earthly Jerusalem, have been moved; first in heart, afterwards by exile. When they were moved in heart and fell, then they crucified the King of the heavenly Jerusalem herself; they were already spiritually without, and shut out of doors their very King. For they cast Him out without their city, anti crucified Him without. He too cast them out of His city, that is, of the everlasting Jerusalem, ...
4. What is this Jerusalem? He briefly describes it. "The mountains stand around Jerusalem" (ver. 2). Is it anything great, that we are in a city surrounded by mountains? Is this the whole of our happiness, that we shall have a city which mountains surround? Do we not know what mountains are? or what are mountains save swellings of the earth? Different then from these are those mountains that we love, lofty mountains, preachers of truth, whether Angels, or Apostles, or Prophets. They stand around Jerusalem; they surround her, and, as it were, form a wall for her. Of these lovely and delightful mountains Scripture constantly speaketh. ...They are the mountains of whom we sing: "I lifted up mine eyes unto the mountains, from whence my help shall come:" because in this life we have help from the holy Scriptures. And through the mountains that receive peace, the little hills received righteousness: for what saith he of the mountains themselves? He said not, they have peace from themselves, ...
About it. Coming from Joppe, travellers cannot see the city till they are very near it, though with respect to Judea, it is very elevated. Hence Josephus styles it "the navel of the land. "(Jewish Wars iii. 2., or 4.)
The construction of the Vulgate is very natural. (Calmet)
For the promise regards the inhabitants, rather than the place, as Hebrew would insinuate.
Lord. Zacharias ii. 5. Heresiarchs have in vain risen up against the Church, though they were able men, like mountains. (St. Augustine) ...