Matthew 21:32
For John came to you in the way of righteousness, and you did not believe him, but the tax collectors and the prostitutes believed him. And even when you saw it, you did not afterward change your minds and believe him. The application of the two-sons parable to John's ministry: the chief priests and elders who received John's message did not believe it; the tax collectors and prostitutes who were not expected to believe it did. The even when you saw it — even when they witnessed the transformation in the lives of those who responded to John — they still did not change their minds. The sealed heart that refuses the evidence is the fully-hardened heart.