4 “Let them be turned away backward and blush that think evil things to me”. At first there was the assault of them persecuting, now there has remained the malice of them thinking. In fact, there are in the Church distinct seasons of persecutions following one another. There was made an assault on the Church when kings were persecuting: and because kings had been foretold as to persecute and as to believe, when one had been fulfilled the other was to follow. There came to pass also that which was consequent; kings believed, peace was given to the Church, the Church began to be set in the highest place of dignity, even on this earth, even in this life: but there is not wanting the roar of persecutors, they have turned their assaults into thoughts.
In these thoughts, as in a bottomless pit, the devil has been bound, he roars and breaks not forth. For it has been said concerning these times of the Church, “The sinner shall see, and shall be angry.” And shall do what? That which he did at first? Drag, bind, smite? He does not this. What then? “With his teeth he shall gnash, and shall pine away.” And with these men the Martyr is, as it were, angry, and yet for these men the Martyr prays. For in like manner as he has wished well to those men concerning whom he has said, “Let them be confounded and fear that seek my soul:” so also now, “Let them be turned backward, and blush, that think evil things to me.”
Wherefore? In order that they may not go before, but follow. For he that censures the Christian religion, and on his own system wills to live, wills as it were to go before Christ, as though He indeed had erred and had been weak and infirm, because He either willed to suffer or could suffer in the hands of the Jews; but that he is a clever man for guarding against all these things; in shunning death, even in basely lying to escape death, and slaying his soul that he may live in body, he thinks himself a man of singular and prudent measures.
He goes before in censuring Christ, in a manner he outstrips Christ: let him believe in Christ, and follow Christ. For that which had been desired but now for persecutors thinking evil things, the same the Lord Himself said to Peter. Now in a certain place Peter willed to go before the Lord....A little before, “Blessed are you, Simon Bar-jona, for flesh and blood has not revealed it to you, but My Father which is in Heaven:” now in a moment, “Go back behind Me, Satan.” What is, “Go back behind Me”?
Follow Me. You will to go before Me, you will to give Me counsel, it is better that thou follow My counsel: this is, “go back,” go back behind Me. He is silencing one outstripping, in order that he may go backward; and He is calling him Satan, because he wills to go before the Lord. A little before, “blessed;” now, “Satan.” Whence a little before, “blessed”? Because, “to you,” He says, “flesh and blood has not revealed it, but My Father which is in Heaven.” Whence now, “Satan”?
Because “you savour not,” He says, “the things which are of God, but the things which are of men.” Let us then that would duly celebrate the nativities of the Martyrs, long for the imitation of the Martyrs; let us not wish to go before the Martyrs, and think ourselves to be of better understanding than they, because we shun sufferings in behalf of righteousness and faith which they shunned not. Therefore be they that think evil things, and in wantonness feed their hearts, “turned backward and blush.” Let them hear from the Apostle afterwards saying, “But what fruit had ye some time in those things at which you now blush?”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)