12 “The Lord on Your right hand”. The Lord had said, “Sit on My right hand;” now the Lord is on His right hand, as if they changed seats....That very Christ, the “Lord on Your right hand,” unto whom You have sworn, and it will not repent You: what does He, Priest for evermore? What does He, who is at the right hand of God, and intercedes for us, like a priest entering into the inner places, and into the holy of holies, into the mysteries of heaven, He alone being without sin, and therefore easily purifying from sins. He therefore “on Your right hand shall wound even kings in the day of His wrath.”
What kings, do you ask? Have you forgotten? “The kings of the earth stood up, and the rulers took counsel together against the Lord, and against His Anointed.” These kings He wounded by His glory, and by the weight of His Name made kings weak, so that they had not power to effect what they wished. For they strove amain to blot out the Christian name from the earth, and could not; for “Whosoever shall fall on this stone shall be broken.” Kings therefore fall on this “stone of offense,” and are therefore wounded, when they say, Who is Christ?
I know not what Jew or what Galilean He may have been, who died, who was slain in such a manner! The stone is before your feet, lying, so to speak, mean and humble: therefore by scorning thou dost stumble, by stumbling you fall, by falling you are wounded....“But on whomsoever it shall fall, it will grind him to powder.” When therefore any one falls upon it, it lies as it were low; it then wounds: but when it shall grind him to powder, then it will come from above. See how in these two words, it shall wound him and grind him to powder: he strikes upon it, and it shall come down upon him: are distinguished the two seasons, of the humiliation and the majesty of Christ, of hidden punishment and future judgment.
He will not crush, when He comes, that man whom He does not wound when He lies in a contemptible appearance....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)