Let us see, then, briefly what holy Scripture has to say regarding good and evil, and what answer we are to return to the questions, “How is it that God created evil?” and, “How is He incapable of persuading and admonishing men?” Now, according to holy Scripture, properly speaking, virtues and virtuous actions are good, as, properly speaking, the reverse of these are evil. We shall be satisfied with quoting on the present occasion some verses from the thirty-fourth Psalm, to the following effect: “They that seek the Lord shall not want any good thing.
Come, you children, hearken unto me; I will teach you the fear of the Lord. What man is he that desires life, and loves many days, that he may see good? Keep your tongue from evil, and your lips from speaking guile. Depart from evil, and do good.” Now, the injunctions to “depart from evil, and to do good,” do not refer either to corporeal evils or corporeal blessings, as they are termed by some, nor to external things at all, but to blessings and evils of a spiritual kind; since he who departs from such evils, and performs such virtuous actions, will, as one who desires the true life, come to the enjoyment of it; and as one loving to see “good days,” in which the word of righteousness will be the Sun, he will see them, God taking him away from this “present evil world,” and from those evil days concerning which Paul said: “Redeeming the time, because the days are evil.”
Source: Against Celsus (New Advent)