Charles H. Spurgeon on Psalms 125:2

As the mountains are round about Jerusalem, so the LORD is round about his people from henceforth even for ever. The hill of Zion is the type of the believer's constancy, and the surrounding mountains are made emblems of the all surrounding presence of the Lord. The mountains around the holy city, though they do not make a circular wall, are, nevertheless, set like sentinels to guard her gates. God doth not enclose his people within ramparts and bulwarks, making their city to be a prison; but yet he so orders the arrangements of his providence that his saints are as safe as if they dwelt behind the strongest fortifications. What a double security the two verses set before us! First, we are established, and then entrenched; settled, and then sentinelled: made like a mount, and then protected as if by mountains. This is no matter of poetry, it is so in fact; and it is no matter of temporary privilege, but it shall be so for ever. Date when we please, "from henceforth" Jehovah encircles his people: look on as far as we please, the protection extends "even for ever." Note, it is not said that Jehovah's power or wisdom defends believers, but he himself is round about them: they have his personality for their protection, his Godhead for their guard. We are here taught that the Lord's people are those who trust him, for they are thus described in the first verses: the line of faith is the line of grace, those who trust in the Lord are chosen of the Lord. The two verses together prove the eternal safety of the saints: they must abide where God has placed them, and God must for ever protect them from all evil. It would be difficult to imagine greater safety than is here set forth.