The abolition of slavery and involuntary servitude – 1865
“Section 1: Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Section 2: Congress shall have power to enforce this article by appropriate legislation.”
While Lincoln’s emancipation proclamation of 1863 freed enslaved people in areas in rebellion against the United States the constitution wasn’t amended until 1865 with the addition of the13th amendment.
See: Previous Amendment (Twelfth Amendment) – Next Amendment (Fourteenth Amendment)