4 And seeing that being delivered over to the lust of his own heart, and predestinated to extreme condemnation, he is to come, by wicked arts, to that vain and empty height and rule; therefore it follows, “For he has said in his heart, I shall not move from generation to generation without evil”: that is, my fame and my name will not pass from this generation to the generation of posterity, unless by evil arts I acquire so lofty a principality, that posterity cannot be silent concerning it. For a mind abandoned and void of good arts, and estranged from the light of righteousness, by bad arts devises a passage for itself to a fame so lasting, as is celebrated even in posterity. And they that cannot be known for good, desire that men should speak of them even for ill, provided that their name spread far and wide. And this I think is here meant, “I shall not move from generation to generation without evil.” There is too another interpretation, if a mind vain and full of error supposes that it cannot come from the mortal generation to the generation of eternity, but by bad arts: which indeed was also reported of Simon, when he thought that he would gain heaven by wicked arts, and pass from the human generation to the generation divine by magic. Where then is the wonder, if that man of sin too, who is to fill up all the wickedness and ungodliness, which all false prophets have begun, and to do such “great signs; that, if it were possible, he should deceive the very elect,” shall say in his heart, “I shall not move from generation to generation without evil”?
5. “Whose mouth is full of cursing and bitterness and deceit”. For it is a great curse to seek heaven by such abominable arts, and to get together such earnings for acquiring the eternal seat. But of this cursing his mouth is full. For this desire shall not take effect, but within his mouth only will avail to destroy him, who dared promise himself such things with bitterness and deceit, that is, with anger and insidiousness, whereby he is to bring over the multitude to his side. “Under his tongue is toil and grief.” Nothing is more toilsome than unrighteousness and ungodliness: upon which toil follows grief; for that the toil is not only without fruit, but even unto destruction. Which toil and grief refer to that which he has said in his heart, “I shall not be moved from generation to generation without evil.” And therefore, “under his tongue,” not on his tongue, because he will devise these things in silence, and to men will speak other things, that he may appear good and just, and a son of God.
6. “He lies in ambush with the rich”. What rich, but those whom he will load with this world's gifts? And he is therefore said to lie in ambush with them, because he will display their false happiness to deceive men; who, when with a perverted will they desire to be such as they, and seek not the good things eternal, will fall into his snares. “That in the dark he may kill the innocent.” “In the dark,” I suppose, is said, where it is not easily understood what should be sought, or what avoided. Now to kill the innocent, is of an innocent to make one guilty.
7. “His eyes look against the poor,” for he is chiefly to persecute the righteous, of whom it is said, “Blessed are the poor in spirit, for theirs is the kingdom of heaven”. “He lies in wait in a secret place, as a lion in his den.” By a lion in a den, he means one in whom both violence and deceit will work. For the first persecution of the Church was violent, when by proscriptions, by torments, by murders, the Christians were compelled to sacrifice: another persecution is crafty, which is now conducted by heretics of any kind and false brethren: there remains a third, which is to come by Antichrist, than which there is nothing more perilous; for it will be at once violent and crafty. Violence he will exert in empire, craft in miracles. To the violence, the word “lion” refers; to craft, the words “in his den.” And these are again repeated with a change of order. “He lies in wait,” he says, “that he may catch the poor;” this has reference to craft: but what follows, “To catch the poor while he draws him,” is put to the score of violence. For “draws” means, he brings him to himself by violence, by whatever tortures he can.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)