What does Matthew 5:47 mean?

Challenging both culture and human nature, Jesus has commanded His disciples to love their enemies. In doing so, they will be imitating God as sons naturally imitate their fathers. After all, God does good for everyone on earth, no matter whether they love Him or hate Him. He provides sun and rain to all (Matthew 5:43–46).

Merely loving your neighbors is not righteous enough to be like God the Father. Nobody is rewarded in the kingdom of heaven for loving people who already love them. Matthew, the former tax collector, included a quip from Jesus in the previous verse: that "even the tax collectors" love others who love them first (Matthew 5:46). It requires no special integrity or faith to love someone who is good to you.

Now Jesus gives an example of what loving an enemy might look like: greeting them! Jesus said that everyone greets their brothers, people who love them. By implication he is saying that only the truly righteous greet those who are opposed to them, meaning their enemies. In this cultural context, to greet someone gladly and mean it required removing any animosity in your heart toward that person. Someone who greets their enemies in this way is truly demonstrating God's love for everyone. This is a love and righteousness that goes way beyond what is normal for humanity. It's what Jesus expects of His disciples.