1 I believe, brethren, that you remarked and committed to memory the title of this Psalm. “The conversion,” he says, “of Haggai and Zechariah.” These prophets were not as yet in existence, when these verses were sung....But both, the one within a year after the other, began to prophesy that which seems to pertain to the restoration of the temple, as was foretold so long before....“For the temple of God is holy, which temple you are.” Whoever therefore converts himself to the work of this building together, and to the hope of a firm and holy edifice, like a living stone from the miserable ruin of this world, understands the title of the Psalm, understands “the conversion of Haggai and Zechariah.” Let him therefore chant the following verses, not so much with the voice of his tongue as of his life. For the completion of the building will be that ineffable peace of wisdom, the “beginning” of which is the “fear of the Lord:” let him therefore, whom this conversion builds together, begin thence.
2. “Blessed is the man that fears the Lord: he will have great delight in His commandments”. God, who alone judges both truthfully and mercifully, will see how far he obeys His commandments: since “the life of man on earth is a temptation,” as holy Job says. But “He who judges us is the Lord.”...He therefore will see how far each man profits in His commandments; yet he who loves the peace of this building together, shall have great delight in them; nor ought he to despair, since there is “peace on earth for men of good will.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)