As I was studying this topic, I made a few interesting discoveries. For one, the words "enemy" and "enemies" are predominately found in the Old Testament. "Enemy" occurs in 95 verses there, as compared to 11 verses in the New Testament. The same is true of "enemies"; it is 245 to 19! This is not surprising in that, in the Old Testament, the Hebrew children were fighting both human and spiritual enemies. In the New Testament, the Lord tells His children to let Him do the fighting (Mt. 22:44; Mk. 12:36; Lk. 1:71-74; 20:43; 1 Cor. 15:25; Heb. 1:13; 10:13; etc.).
Jesus said, "Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you" (Mt. 5:43-44). While the concept of "loving one's enemies" was viewed to be a "new teaching" of Jesus, it is also found in the Old Testament.
In the Book of Proverbs, we read, "Rejoice not when thine enemy falleth, and let not thine heart be glad when he stumbleth" (Prov. 24:17). And again, "If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink" (Prov. 25:21). Unfortunately, the writer of Proverbs was not motivated by love for his enemies, as can be seen by the verses following these quotes. "Lest the LORD see it, and it displease Him, and He turn away His wrath from Him" (Prov. 24:18); and "For thou shalt heap coals of fire upon his head, and the LORD shall reward thee" (Prov. 25:22).
We should pray for those who oppose God, as we ourselves were once His enemies (Rom. 5:10; Col. 1:21; etc.). And who are the enemies of God? They are all who will not submit to His reign over their lives (Lk. 19:27)! In reality, the one enemy nearly all believers fear, is what the Bible calls "the last enemy": death (1 Cor. 15:26). But based upon our eternal relationship with God as our Father, we have no need to fear death; in fact, like Paul, we ought to look forward to it (2 Cor. 5:1-8)!
Death, for the believer, is nothing more than a metamorphosis into Christ-likeness!