14 But what is it that he next adds? “Let the wickedness of his fathers be had in remembrance in the sight of the Lord, and let not the sin of his mother be done away”. Is it to be understood, that even the sins of his fathers shall be visited upon him? For upon him they are not visited, who has been changed in Christ, and has ceased to be the child of the wicked, by not having imitated their conduct....And to these words, “I will visit the sins of the fathers upon the children,” is added, “who hate Me;” that is, hate Me as their fathers hated Me: so that as the effect of imitating the good is that even their own sins are blotted out, so the imitation of the wicked causes men to suffer not their own deservings only, but those also of those whom they have imitated....
15. “Let them always be against the Lord”. “Against the Lord,” means in the Lord's sight: for other translators have rendered this line, “let them be always in the sight of the Lord;” while others have rendered it, “let them be before the Lord always;” as it is elsewhere said, “You have set our misdeeds in Your sight.” By “alway,” he means that this great crime should be without pardon, both here, and in a future life. “Let the memorial of them perish from off the earth:” that is, of his father and of his mother. By memorial of them, he means, that which is preserved by successive generations: this he prophesied should perish from the earth, because both Judas himself, and his sons, who were the memorial of his father and mother, without any succeeding offspring, as it is said above, were consumed in the short space of one generation....
16. “And that, because he remembered not to act mercifully”; either Judas, or the people itself. But “remembered not” is better understood of the people: for if they slew Christ, they might well remember the deed in penitence, and act mercifully towards His members, whom they most perseveringly persecuted. For this reason he says, “but persecuted the poor man and the beggar”. It may indeed be understood of Judas; for the Lord did not disdain to become poor, when He was rich, that we might be enriched by His poverty. But how shall I understand the word “beggar,” save perhaps because He said to the Samaritan woman, “Give me to drink,” and on the Cross He said, “I thirst.” But as to what follows, I do not see how it can be understood of our Head Himself, that is, the Saviour of His own body, whom Judas persecuted. For after saying, “He persecuted the poor man and the beggar:” he adds, “and to slay,” that is, “that he might slay Him,” for some have so rendered it, “Him that was pricked at the heart.” This expression is not commonly used except of the stings of past sins in the sorrows of penitence; as it is said of those who, when they had heard the Apostles after our Lord's ascension, were “pricked in heart,” even they who had slain the Lord....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)