1 “Out of the deep have I called unto You, O Lord: Lord, hear my voice”. Jonas cried from the deep; from the whale's belly. He was not only beneath the waves, but also in the entrails of the beast; nevertheless, those waves and that body prevented not his prayer from reaching God, and the beast's belly could not contain the voice of his prayer It penetrated all things, it burst through all things, it reached the ears of God: if indeed we ought to say that, bursting through all things, it reached the ears of God, since the ears of God were in the heart of him who prayed. For where has not he God present, whose voice is faithful? Nevertheless, we also ought to understand from what deep we cry unto the Lord. For this mortal life is our deep. Whoever has understood himself to be in the deep, cries out, groans, sighs, until he be delivered from the deep, and come unto Him who sits above all the deeps....For they are very deep in the deep, who do not even cry from the deep. The Scripture says, “When the wicked has reached the depth of evils, he despises.” Now consider, brethren, what sort of deep that is, where God is despised. When each man sees himself overwhelmed with daily sins, pressed down by heaps and weights, so to speak, of iniquities: if it be said unto him, Pray unto God, he laughs. In what manner? He first says, If crimes were displeasing unto God, should I live? If God regarded human affairs, considering the great crimes which I have committed, should I not only live, but be prosperous? For this is wont to happen to those who are far in the deep, and are prosperous in their iniquities: and they are the more plunged in the deep, in proportion as they seem to be more happy; for a deceitful happiness is itself a greater unhappiness....
2. “Lord, hear my voice. O let Your ears consider well the voice of my complaint”. Whence does he cry? From the deep. Who is it then who cries? A sinner. And with what hope does he cry? Because He who came to absolve from sins, gave hope even to the sinner down in the deep. What therefore follows after these words: “If Thou, Lord, will be extreme to mark what is amiss, O Lord, who may abide it?”. So, he has disclosed from what deep he cried out. For he cries beneath the weights and billows of his iniquities....He said not, I may not abide it: but, “who may abide it?” For he saw that near the whole of human life on every side was ever bayed at by its sins, that all consciences were accused by their thoughts, that a clean heart trusting in its own righteousness could not be found.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)