3 But now ye do what? Why these things to you do I speak? “Because in heart iniquities ye work on earth”. Iniquities perchance in heart alone? Hear what follows: both their heart hands do follow, and their heart hands do serve, the thing is thought of, and it is done; or else it is not done, not because we would not, but because we could not, Whatever you will and canst not, for done God does count it. “For in heart Iniquities ye work on earth.” What next?
“Iniquities your hands knit together.” What is, “knit together”? From sin, sin, and to sin, sin, because of sin. What is this? A theft a man has committed, a sin it is: he has been seen, he seeks to slay him by whom he has been seen: there has been knit together sin with sin: God has permitted him in His hidden judgment to slay that man whom he has willed to slay: he perceives that the thing is known, he seeks to slay a second also; he has knit together a third sin: while these things he is planning, perchance that he may not be found out, or that he may not be convicted of having done it, he consults an astrologer; there is added a fourth sin: the astrologer answers perchance with some hard and evil responses, he runs to a soothsayer, that expiation may be made; the soothsayer makes answer that he is not able to expiate: a magician is sought.
And who could enumerate those sins which are knit together with sins? “Iniquities your hands do knit together.” So long as you knit together, you bind sin upon sin. Loose yourself from sins. But I am not able, you say. Cry to Him. “Unhappy man I, who shall deliver me from the body of this death?” For there shall come the Grace of God, so that righteousness shall be your delight, as much as you delighted in iniquity; and you, a man that out of bonds has been loosed, shall cry out to God, “You have broken asunder my bonds.” “You have broken asunder my bonds,” is what else but, “You have remitted my sins”?
Hear why chains they are: the Scripture makes answer, “with the chains of his sins each one is bound fast.” Not only bonds, but chains also they are. Chains are those which are made by twisting in: that is, because with sins sins you were knitting together....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)