6 “Preserve me, O Lord, from the hand of the sinner, from unrighteous men deliver me”. Here they wear their real colours, they are known; here we have no need to understand, but to act: we have need to pray, not to ask who they are. But how you should pray against such men, he explains in what follows. For many pray unskilfully against wicked men. “Who have imagined,” says he, “to trip up my steps.” Thus far it may be understood carnally. Every one has enemies, who seek to cheat him in trade, to rob him of money, where they are engaged together in business; every one has some neighbour his enemy, who devises how to bring mischief upon his family, to injure in some way his property and surely he devises this by deceit, by fraud, by devilish devices he endeavours to accomplish this: no one can doubt it.
Yet not for these reasons are they to be guarded against, but lest they lay in wait for you and draw you to themselves, that is, separate you from the Body of Christ, and make you of their body. For as Christ is the Head of the good, so is the devil their head. What is, “to trip up my steps”? Not as though you should be deceived in the business you have with him, or he cheat you in a case which you have with him in the law courts. He has “tripped up your steps,” if he have hindered you in the way of God; so that what you directed aright may stumble, or fall from the way, or fall in the way, or draw back from the way, or stop on the way, or go back to the place from whence it had come.
Whatsoever has done this to you, has tripped you up, has deceived you. Against such snares as these pray thou, lest you lose your heavenly inheritance, lest you lose Christ your Joint-heir, for you are destined to live for ever with Him, who has made you an heir. For you are made an heir, not by one whom you are to succeed after his death, but One together with whom you are to live for ever.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)