For anyone unaware, that is nearly[1] the entirety of the text of the 13th Amendment to the US Constitution from 1865. This exception is rather (in)famous. I remember being quizzed on it in an elementary or middle school history or social studies class.

[1] the only excluded bit is the followup "Congress shall have power to enforce this article by appropriate legislation." Without this, the power to enforce the 13th Amendment would be left up to the states due to the 10th Amendment ("The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people."), which would have slightly useless given the whole war that had just been fought over some states wanting to keep slavery.