The Hebrew verb ayav (אָיַב) means to be hostile, to act as an enemy, or to become an enemy to someone. The active participle oyev (H341) is the standard Hebrew word for 'enemy,' and its prevalence in the Psalms and Old Testament narratives reflects the serious reality of enmity in the ancient world.
The verb is used to describe both human hostility and Israel's relationship with surrounding nations who opposed them. It can also describe a spiritual state — being in opposition to God or to God's people.
The concept of enmity runs through the entire Bible, from the first enmity placed between the serpent and the woman (Genesis 3:15) to the final defeat of all enemies at the end of Revelation. The Psalms are full of cries for deliverance from oyevim (enemies), reflecting the real warfare of the life of faith.
Jesus' teaching on enemies is one of the most radical elements of the Gospel: 'Love your enemies' (Matthew 5:44). This completely overturns the natural human response to hostility. The cross itself is the supreme act of enemy-love — 'While we were enemies, we were reconciled to God through the death of his Son' (Romans 5:10). God does not merely tolerate His enemies; in Christ, He transforms them into friends (John 15:15).