What does Matthew 5:43 mean?
This statement is subtly different from Jesus' prior comments about teachings from the scribes and Pharisees. Up to now, statements such as "you shall not murder" (Matthew 5:21) and "you shall not commit adultery" (Matthew 5:27) were legitimate commands given by God in the Old Testament. Jesus' intent in using "but I say…" in response was not to reject those teachings; it's to move them beyond shallow, legalistic, unloving interpretations (Matthew 5:22, 28). Here, however, the teaching Jesus presents includes a detail God never gave the people of Israel.God never commands hate for other people. Leviticus 19:18 commands love for one's neighbor, but there's no Scripture where Jesus' listeners would have been told to hate their enemies. It's possible that Israel's religious leaders seized on the "neighbor" concept, claiming that those who were not their "neighbors" were not to be loved. Religious leaders might have taught, since God hates evil, that hatred toward the wicked enemies of God was not only justified, but required.
In Jesus' earthly ministry, He clarified that loving one's neighbor was the second-greatest of all God's commandments (Matthew 22:36–39). He also expanded the definition of one's "neighbor" (Luke 10:29) well beyond the cultural norm through the parable of the good Samaritan (Luke 22:36–37). That doesn't mean this is easy; It's hard to love other people. Jesus, though, will show that loving one's enemies can truly be powerful when done as a representative of God.
Once again, Jesus flips the common understanding of righteousness on its head. Jesus' original audience probably wondered how any person could possibly be righteous, if a person must love His enemies. That, of course, is part of the point Jesus intends to make (Matthew 5:48). While we ought to strive to meet God's standards, only salvation by grace through faith can bring us into heaven (Titus 3:5).