Summary: How can we show love to the one who hates us?
"Love your neighbor" is the commandment given by God in Leviticus 19:18 . But "Hate your enemies" is not a commandment (nowhere written in OT) but addition/alteration made by Pharisees and Scribes. That’s why Jesus said, '"you have heard" and not "it is written".
1. Who is our enemy?
Spiritually a believer can't have any enemy because we have been commanded to love others. But it is quite possible that others may hate, harm or persecute us or wish evil of us. They are not our enemies but we may be enemies to them.
a. The Devil:
I Peter 5:8-9- In a true sense we have only one enemy, the greatest of all, Satan. We should really hate our spiritual enemy and not love him.
b. Those who persecute us (Mathew 5:44)
By "enemy" he means people who oppose you and try to hurt you. "Persecute" means to pursue with harmful intentions. It might include very severe hostility like the hostility Jesus faced.
c. Those who are evil, behaving against God, defying God's commandments and laws (Mathew 5:45b)
Romans 5:10- A person who is not born again or reconciled with God is His enemy
Philippians 3:18-19- The enemies of the cross. Three characteristics are: whose fate is destruction, whose god is their belly [their worldly appetite, their sensuality, their vanity], and whose glory is in their shame—who focus their mind on earthly and temporal things.
Psalms 139:20-22- David defined God's enemies:
They speak of you with evil intent; your adversaries misuse your name. Do I not hate those who hate you, Lord, and abhor those who are in rebellion against you?
The evil and the unrighteous are people who defy the laws of God. They resist his will. They do not submit to his authority.
d. Anyone Who Doesn't Love us or Is Not our Brother (Mathew 5:46-47)
Here in verse 46 the "enemy" is any one who doesn't love you. "If you (just) love those who love you, you are not loving the way I just commanded." And in verse 47 the "enemy" is anyone who is not your brother. "If you greet your brothers only, you are not loving the way I just commanded you."
2. The motivation for loving enemies:
a. Perfect God loves both kinds of people -good and evil (Mathew 5:45)
Because God's love is indiscriminate love, shown equally to good men and bad. Calvin calls it a "common grace" for believers and unbelievers- sunlight and rain available for both categories. In case of accidents or calamities, both categories are killed.
The "common grace" is for all but "saving grace" is shown to the repenting sinners only.
We should follow God's standard of love. We are to love others (including our friends and enemies) like God, not like men.
Romans 5:8, 10- God's love to us, while we were sinners (enemies of God) Christ died for us.
5:46- Human love is imperfect even though noblest and the best as it is contaminated with some degree of self-interest. I love you and expect your love in return.
5:47- If we greet our brothers only, we are not better than pagans or non-Christians.
Our love standard has to be superior to that of the sinners and non-Christians. Loving enemies is impossible without the supernatural grace and power from the Holy Spirit.