6 What does the Psalm add? “In His hand are all the corners of the earth”: we recognise the corner stone: the corner stone is Christ. There cannot be a corner, unless it has united in itself two walls: they come from different sides to one corner, but they are not opposed to each other in the corner. The circumcision comes from one side: the uncircumcision from the other; in Christ both peoples have met together: because He has become the stone, of which it is written, “The stone which the builders rejected, has become the head of the corner.”...
7. “For the sea is His and He made it”. For the sea is this world, but God made also the sea: nor can the waves rage save only so far as to the shore, where He has marked their bounds. There is therefore no temptation, that has not received its measure....“And His hands prepared the dry land.” Be thou the dry land: thirst for the grace of God: that as a sweet shower it may come upon you, may find in you fruit. He allows not the waves to cover what He has sown. “And His hands prepared the dry land.” Hence also therefore let us shout unto the Lord.
8. “O come, let us worship, and fall down to Him; and mourn before the Lord our Maker”....Perhaps you are burning with the consciousness of a fault; blot out with tears the flame of your sin: mourn before the Lord: fearlessly mourn before the Lord, who made you; for He despises not the work of His own hands in you. Think not you can be restored by yourself. By yourself you may fall off, you can not restore yourself: He who made you restores you. “Let us mourn before the Lord our Maker:” weep before Him, confess unto Him, prevent His face in confession. For who are you who mournest before Him, and confessest unto Him, but one whom He created? The thing created has no slight confidence in Him who created it, and that in no indifferent fashion, but according to His own image and likeness.
9. “For He is the Lord our God”. But that we may without fear fall down and kneel before Him, what are we? “We are the people of His pasture, and the sheep of His hand.” See how elegantly he has transposed the order of the words, and as it were not given its own attribute to each word; that we may understand these very same to be the sheep, who are also the people. He said not, the sheep of His pasture, and the people of His hand; which might be thought more congruous, since the sheep belong to the pasture; but He said, “the people of His pasture.” The people are therefore sheep, since he says, “the people of His pasture:” the people themselves are sheep....He praises these sheep also in the Song of Solomon, speaking of some perfect ones as the teeth of His Spouse the Holy Church: “Your teeth are like a flock of sheep that are even shorn, which come up from the washing; whereof every one bears twins, and there is none barren.” What means, “Your teeth”? These by whom you speak, for the teeth of the Church are those through whom she speaks. Of what sort are your teeth? “Like a flock of sheep that are shorn.” Why, “that are shorn”? Because they have laid aside the burdens of the world. Were not those sheep, of which I was a little before speaking, shorn, whom the bidding of God had shorn, when He says, “Go and sell that you have, and give to the poor; and you shall find treasure in heaven: and come and follow Me”? They performed this bidding: shorn they came. And because those who believe in Christ are baptized, what is there said? “which come up from the washing;” that is, come up from the cleansing. “Whereof every one bears twins.” What twins? Those two commandments, wherefrom hang all the Law and the Prophets.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)