18 But what is, “Depart from evil”?. It is little that thou injure none, murder none, steal not, commit not adultery, do no wrong, speak no false witness; “Depart from evil.” When you have departed, you say, Now I am safe, I have done all, I shall have life, I shall see good days. Not only says he, “Depart from evil,” but also, “and do good.” It is nothing that thou spoil not: clothe the naked. If you have not spoiled, you have declined from evil; but you will not do good, except thou receive the stranger into your house. So then depart from evil, as to do good. “Seek peace, and ensue it.” He has not said, You shall have peace here; seek it, and ensue it. Whither shall I ensue it? Whither it has gone before. For the Lord is our peace, has risen again, and has ascended into Heaven. “Seek peace, and ensue it;” because when thou also hast risen, this mortal shall be changed, and you shall embrace peace there where no man shall trouble you. For there is perfect peace, where you will not hunger....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)