24 “Arise, Lord, and attend to My judgment”. To what judgment? That You are in tribulation; that You are tormented with labours and pains? Do not even many wicked men suffer the same? To what judgment? Therefore are You righteous, because Thou sufferest these things? No: but what? “To My judgment.” What follows? “Attend to My judgment; even to My cause, My God, and My Lord.” Not to My punishment, but to My cause: not to that which the robber has in common with Me, but to that whereof is said, “Blessed are they which are persecuted for righteousness' sake.” For this cause is distinguished.
For punishment is equal to good and bad. Therefore Martyrs, not the punishment, but the cause makes, for if punishment made Martyrs, all the mines would be full of Martyrs, every chain would drag Martyrs, all that are executed with the sword would be crowned. Therefore let the cause be distinguished; let none say, because I suffer, I am righteous. Because He who first suffered, suffered for righteousness' sake, therefore He added a great exception, “Blessed are they which are persecuted for righteousness' sake.”
For many having a good cause do persecution, and many having a bad cause suffer persecution. For if persecution could not be done rightly, it had not been said in a certain Psalm, “Whoso privily slanders his neighbour, him did I persecute.”...Let none then say, I suffer persecution: let him not sift the punishment, but prove the cause: lest if he prove not the cause, he be numbered with the ungodly. Therefore how watchfully, how excellently has This Man recommended Himself, “O Lord, attend to My judgment,” not to My punishments; “even to My cause, My God, and My Lord.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)