4 So then if the adversary brought this charge, we ought to fear lest it be brought against us. For with a very slanderous accuser have we to deal. If he seek to invent what is not, how much more will he seek to object what really is. Nevertheless let us rejoice, that ours is such a Judge, as cannot be deceived by our accuser. For if we had a man for our judge, the enemy might invent for him what he would. For none is more subtle in invention than the devil. For he it is who at this time also invents all false accusations against the saints.
He knows his accusations can have no avail with God, and so He scatters them among men. Yet what does this profit him, seeing the Apostle says, “Our glorying is this, the testimony of our conscience?” Yet think ye that he does not invent these false charges with anything of subtlety? Yes, well he knows what evil he shall work thereby, if the watchfulness of faith resist him not. For for this reason scatters he his evil charges against the good, that the weak may think that there are no good, and so may give themselves up to be hurried along, and made a prey of by their lusts, while they say within themselves, “For who is there that keeps the commandments of God, or who is there that preserves chastity?” and while he thinks that no one does, he himself becomes that no one.
This then is the devil's art. But such a man was Job, that he could not invent any such charge against him; for his life was too well known and manifest. But because he had great riches, he brought that against him, which if it had any existence, might lie in the heart, and not appear in the conduct. He worshipped God, he gave alms; and with what heart he did this none knew, no not the Devil himself; but God had known. God gives His testimony to His own servant; the Devil calumniates the servant of God.
He is allowed to be tried, Job is proved, the Devil is confounded. Job is found to worship God for His Own sake, to love Him for His Own sake; not because He gave him ought, but because He did not take away Himself. For he said, “The Lord gave, the Lord has taken away; as it seemed good to the Lord, so is it done, blessed be the Name of the Lord.” The fire of temptation approached him; but it found him gold, not stubble; it cleared away the dross from it, but did not reduce it to ashes.
Source: Sermons on Selected Lessons of the New Testament (New Advent)