What does Matthew 15:3 mean?

A group of Pharisees—legalistic, tradition-minded religious leaders—have come all the way from Jerusalem to Galilee to discredit Jesus. They have pointed out that Jesus does not require His disciples to practice a specific form of ritual handwashing before eating. This traditional practice of the Jewish people was not, itself, a command of God. However, it was part of the extensive teachings of Israel's religious leaders. Adherence to those minute details was one of the ways groups such as the Pharisees measured their religiosity.

Jesus doesn't even bother to address the main accusation. Jesus is not falling for the rhetorical trap: explaining why He breaks a tradition which is not part of godly command. Instead, Jesus flips the table on these Pharisees and asks why they break an actual command from God for the sake of a tradition!

The following verses will spell out what command and tradition Jesus is referring to. Among the dangers of tradition-minded religious practice and legalism is missing the actual instructions of God, including the intent behind those directives. In the example Jesus gives, a command to care for other people has been neutralized by human legalism (Matthew 15:4–6).