That one's speech reveals one's heart may represent conventional Jewish wisdom (compare Dalman 1929:227); Jesus here indicates that even the most careless words spoken without thought will testify concerning one's character in the judgment day. God does not listen only to what we say during Sunday-morning church services.

In this context Jesus is saying that one expects people like these Pharisees to blaspheme the Holy Spirit because their hearts are so corrupt. Because the Pharisees appeared righteous to most other observers (compare Lk 16:15), Jesus' harsh condemnation of their behavior sounds an even greater warning to those today who reject the truth of Christ yet sit in churches.