Where does the Prophet say that we will be punished for saying we did not sin?

The Prophet Yirmiyahu, Jeremiah, tells us this very clearly. In his prophecy, HaKadosh Baruch Hu says that He will punish us not merely for the sin itself, but specifically because we claimed we did not sin. The Prophet states that Hashem enters into judgment with us because we denied our transgressions, saying "I didn't sin" or "I haven't done anything wrong." This is an extremely serious matter. When a person becomes so accustomed to sinning that he no longer recognizes it as a sin - when he thinks his violations are actually permissible or even good - this denial itself becomes a separate and severe punishment. The Prophet is teaching us that the very act of denying our sins, of claiming innocence when we are guilty, brings additional Divine judgment upon us. This concept appears elsewhere as well - we see that Bilaam knew that once punishment arrived, the way to possibly save himself was through vidui, admitting his guilt. He understood that trying to deny the sin would not help him. Only by acknowledging "I have sinned" could he hope for mercy from Hashem. The bottom line is clear: Hashem punishes us for our transgressions, but He punishes us even more severely when we refuse to acknowledge them and claim we are innocent.