What does Matthew 5:46 mean?

Jesus has commanded His disciples to love their enemies and to demonstrate that love, in part, by praying even for those who persecute them (Matthew 5:43–45). This is the level of righteousness God desires from those who want to enter the kingdom of heaven (Matthew 5:48). If that seems like an impossible standard, it is: part of the gospel message is that no person's good deeds can ever earn eternal salvation (Romans 3:10; Titus 3:5).

Even from a worldly, unspiritual perspective, everyone loves the people who love them. Nobody gets a reward for that in the kingdom of God. It's easy, and it requires nothing. Jesus says this is so easy that even "tax collectors" do it.

The apostle Matthew is writing this story of Jesus' life, and he was a tax collector for the Romans before Jesus called him (Matthew 9:9). These men gathered taxes, ultimately for the Roman occupiers. That, alone, made them hated among their Jewish brothers, who saw them as collaborators and traitors. The job also lent itself to deep corruption: as employees of the Roman government, tax collectors often lined their own pockets by collecting more than was actually due. Such men became wealthy at the expense of their fellow citizens.

Jesus' declaration that "even tax collectors" can love those who love them was meant as a challenge. Tax collectors were associated with a lack of integrity, poor morals, and no loyalty. Even "those people" find it easy to love family and close friends. Loving your enemies, though, requires imitation of God Himself since it is such an unnatural thing for human beings to do.