What does Matthew 22:39 mean?

The Pharisee who tested Jesus did not ask about the "two greatest commandments." He asked for Jesus' take on which was the single greatest (Matthew 22:34–38). Jesus, though, decides the second commandment is so essential that it must be mentioned along with the first one.

Both commands focus solely on what a person does with his or her affection and attention and actions. The greatest command is to love God with every aspect of our being. It comes from Deuteronomy 6:5. The second greatest commandment comes from Leviticus 19:18. Jesus says that it is similar to the first commandment, likely because it is about who and how we love: You shall love your neighbor as yourself.

The second greatest commandment assumes an obvious fact of human nature: that human beings naturally love and care for themselves. This perspective is the basis for what has come to be known as the Golden Rule. Jesus taught this in His sermon on the mount (Matthew 5:1–2), and it helps to explain what it means to love another as we love ourselves: "So whatever you wish that others would do to you, do also to them" (Matthew 7:12).

This first and second commandment were woven deeply into Judaism and Jewish life. It's unlikely that anyone was greatly surprised by Jesus' answer to what is the greatest commandment, but the fact that He gave it makes the answer meaningful for all time.