5 But suppose the penalty were exacted for our listlessness in our solemn assemblies what would our condition be? For this ye cannot but know, that often while God Himself is addressing us all by His prophet, we are holding frequent and long conversations with those near us, about matters which in no way concern us. Passing by, then, all the rest, should He choose to exact of us the penalty due for this sin only, what hope of salvation will there be? For do not suppose that this offense is a small one, but if you would be aware of its magnitude, examine how this very thing is regarded among men, and then you will perceive the enormity of the sin.
Just venture, when some magistrate is talking to you, or rather some friend who is of somewhat superior dignity, to turn from him, and enter into conversation with your servant; and you will then perceive, what you venture on in dealing thus with God! For if he be any one of the more distinguished classes, he will even demand reparation of you for such an insult. Yet God, while He is treated with as great, and still greater contempt than this, every day; and that not by one, or two, or three persons, but by almost all of us; is still forbearing and longsuffering, not in regard to this alone, but to other things which are far more grievous.
For these things are what must be admitted, and what are obvious to all, and by almost all men they are daringly practised. But there are yet others, which the conscience of those who commit them is privy to. Surely, if we were to think of all this; if we were to reason with ourselves, supposing even that we were the cruelest and harshest of men, yet upon taking a survey of the multitude of our sins, we should for very fear and agony be unable to remember the injury done by others towards ourselves.
Bear in mind the river of fire; the envenomed worm; the fearful Judgment, where all things shall be naked and open! Reflect, that what are now hidden things, are then to be brought to light! But should you pardon your neighbour all these sins which till then await their disclosure are done away with here; and when you shall depart this life, you will not drag after you any of that chain of transgressions; so that you receive greater things than you give. For many such transgressions, indeed, we have often committed, which no other person knows; and when we think, that on That Day these our sins shall lie exposed to the eyes of all, upon the public theatre of the universe, we are in pain beyond any punishment, being choked and strangled by our conscience.
Yet this shame, great as it is; these sins, these punishments, great as they are; there is a possibility of purging away through forgiveness exercised toward our neighbour.
Source: Homilies on the Statues (New Advent)