Tractate Horayot
The Gemara Horayot is the study of the laws relating to the inadvertent teaching ordered by a court (i.e. they erred in the law and the reverse order of the knowledge of the Torah), as well as the laws of a high priest or a king who sinned by mistake.
The Horayot tractate is a gemara which contains 3 chapters. It is the shortest gemara tractate in the Babylonian Talmud at only 14 pages.