Clause 1. Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.
The Framers of the Constitution took treason seriously. It was the one and only crime specifically defined in the Constitution. The requirement for two eyewitnesses to an overt act of treason to convict someone for the crime remains an odd wrinkle in the law today.
Clause 2. The Congress shall have Power to declare the Punishment of Treason, but no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted.
Corruption of Blood! That sounds exciting. All it means is that the government cannot punish the relatives or descendents of someone convicted of treason; the maximum punishment for committing treason is death. In actual practice, the United States has never executed anyone for committing treason.