In a reflection on Psalm 25, D.A. Carson has the following to say:
ONE OF THE STRIKING FEATURES OF the Psalms, especially the psalms of David, is the theme of enemies. This makes some Christians nervous. Does not the Lord Jesus tell us to love our enemies (Matt. 5:43–47)? Yet here David prays that God will not let his enemies triumph over him (Ps. 25, especially v. 1), calls them “treacherous” (Ps. 25:3), and complains that they have increased and fiercely hate him (Ps. 25:19). It is inadequate to ascribe the two stances to differences between the new covenant and the old.
Preliminary reflections include:
(1) Even Jesus’ teaching that his followers love their enemies presupposes that they have enemies. Jesus’ requirement that we love our enemies must not be reduced to the sentimental notion that we all become so “nice” that we never have any enemies.
(2) New Testament believers may have enemies who must at some level be opposed. The apostle Paul, for instance, says that he has handed Hymenaeus and Alexander over to Satan to teach them not to blaspheme (1 Tim. 1:20). Both 2 Peter 2 and Jude deploy pretty colorful language to denounce fundamental enemies of the Gospel. Even if his language belongs to hyperbole, Paul can wish that the agitators in Galatia would emasculate themselves (Gal. 5:12). The Lord Jesus himself—the same Jesus who, while dying on the cross, cries, “Father, forgive them, for they do not know what they are doing” (Luke 23:34)—can elsewhere denounce his enemies in spectacularly colorful language (Matt. 23). It is difficult to avoid the conclusion that, unless we are to accuse the apostles and Jesus of hypocritical inconsistency, the demand that we love our enemies must not be reduced to the sentimental twaddle that merely smooths enemies out of existence.
(3) A very good case can be made for the view that the primary concern of Matthew 5:43–47 is to overthrow personal retaliation, to eschew the vendetta, to overcome the evil we receive by the good we perform, to absorb the hatred of an opponent and return love. But none of this denies for a moment that the other person is an enemy. Moreover, those in leadership may, out of love, feel obligated to protect the flock by chasing out a wolf in sheep’s clothing, by exposing the charlatan, by denouncing the wicked—without succumbing to personal venom.
(4) One measure of whether one’s response is the hatred of vengeance or something more principled that cherishes God’s holiness and leaves room for forbearance and love, is the set of associated commitments. In David’s case, these include trust (Ps. 25:1–3, 4–5, 7b, 16, 21), repentance and faith (Ps. 25:7, 11, 18), and covenantal fidelity (Ps. 25:10).
via For the Love of God.
See also either or both of these posts:
Addendum: Dr George Guthrie interviews Dr David Howard on the same topic: