What does Matthew 23:31 mean?

Jesus is exposing yet another form of hypocrisy practiced by the scribes and Pharisees. The term "hypocrite" is transliterated from the Greek word hipokritēs, which literally meant stage actors. Those who say one thing, but live something else, are pretenders. Christ has already criticized these men for claiming to honor God, when their actions are legalism and self-honoring (Matthew 23:1–7).

The next form of pretense comes in how these men speak about God's messengers from prior generations. The Pharisees and scribes claimed to honor and celebrate Israel's prophets of old. They believed they would never have joined those who rejected and killed these messengers sent from God to His people Israel. Jesus refutes their arrogance with a rhetorical point which can be hard for modern readers to follow.

As Christ frames it, when the scribes and Pharisees admit their forefathers persecuted God's messengers, they put themselves into the same category of guilt. In that culture, society often placed a sense of guilt on the children of criminals. Jesus points out that these leaders are, by their own admission, the sons of the killers of God's messengers. In a rhetorical sense—by the standards of the day—these men are identifying themselves with enemies of the Lord.

At the same time, Jesus knows that these men are "spiritually" the sons of those murderous ancestors. Their attitudes towards the Son of God prove their spiritual condition (John 8:43–44). The same religious leaders who claim they would have listened to ancient prophets have already rejected John the Baptist (Matthew 23:21–27). Even now they are plotting to have Jesus murdered (John 11:53; Mark 3:6; Luke 22:2).