6 Thus also most pertinently may be understood, “let the mountains bear peace to the people,” namely, that we understand the peace to consist in the reconciliation whereby we are reconciled to God: for the mountains receive this for His people....“Let the mountains, therefore, receive peace for the people, and the hills justice:” so that in this manner, both being at one, there may come to pass that which has been written, “justice and peace have kissed one another.” But that which other copies have, “let the mountains receive peace for the people, and let the hills:” I think must be understood of all sorts of preaching of Gospel peace, whether those that go before, or those that follow after. But in these copies this follows, “in justice He shall judge the poor of the people.” But those copies are more approved of which have that which we have expounded above, “let the mountains bear peace to the people, and the hills justice.” But some have, “to Your people;” some have not to “Your,” but only “to the people.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)