1 Touching this title there is no question. “O Lord who shall sojourn in Your tabernacle?”. Although tabernacle be sometimes used even for an everlasting habitation: yet when tabernacle is taken in its proper meaning, it is a thing of war. Hence soldiers are called tent-fellows, as having their tents together. This sense is assisted by the words, “Who shall sojourn?” For we war with the devil for a time, and then we need a tabernacle wherein we may refresh ourselves. Which specially points out the faith of the temporal Dispensation, which was wrought for us in time through the Incarnation of the Lord. “And who shall rest in Your holy mountain?” Here perhaps he signifies at once the eternal habitation itself, that we should understand by “mountain” the supereminence of the love of Christ in life eternal.
2. “He who walks without stain, and works righteousness”. Here he has laid down the proposition; in what follows he sets it forth in detail.
3. “Who speaks the truth in his heart.” For some have truth on their lips, and not in their heart. As if one should deceitfully point out a road, knowing that there were robbers there, and should say, If you go this way, you will be safe from robbers; and it should turn out that in fact there were no robbers found there: he has spoken the truth, but not in his heart. For he supposed it to be otherwise, and spoke the truth in ignorance. Therefore it is not enough to speak the truth, unless it be so also in heart. “Who has practised no deceit in his tongue”. Deceit is practised with the tongue, when one thing is professed with the mouth, another concealed in the breast. “Nor done evil to his neighbour.” It is well known that by “neighbour,” every man should be understood. “And has not entertained slander against his neighbour,” that is, has not readily or rashly given credence to an accuser.
4. “The malicious one has been brought to nought in his sight”. This is perfection, that the malicious one have no force against a man; and that this be “in his sight;” that is, that he know most surely that the malicious is not, save when the mind turns itself away from the eternal and immutable form of her own Creator to the form of the creature, which was made out of nothing. “But those that fear the Lord, He glorifies:” the Lord Himself, that is. Now “the fear of the Lord is the beginning of wisdom.” As then the things above belong to the perfect, so what he is now going to say belongs to beginners.
5. “Who swears unto his neighbour, and deceives him not.” “Who has not given his money upon usury, and has not taken rewards against the innocent”. These are no great things: but he who is not able to do even this, much less able is he to speak the truth in his heart, and to practise no deceit in his tongue, but as the truth is in the heart, so to profess and have it in his mouth, “yea, yea; nay, nay;” and to do no evil to his neighbour, that is, to any man; and to entertain no slander against his neighbour: all which are the virtues of the perfect, in whose sight the malicious one has been brought to nought. Yet he concludes even these lesser things thus, “Whoso does these things shall not be moved for ever:” that is, he shall attain unto those greater things, wherein is great and unshaken stability. For even the very tenses are, perhaps not without cause, so varied, as that in the conclusion above the past tense should be used, but in this the future. For there it was said, “The malicious one has been brought to nought in his sight:” but here, “shall not be moved for ever.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)