Under what authority did the u. s. supreme court “incorporate” protections in the bill of rights in order to apply them to states

U.s. supreme court “incorporate” protections in the bill of rights in order to apply them to states under: The Fourteenth Amendment’s due process clause 
The Fourteenth Amendment’s due process clause that prevents any states from giving any special treatment toward someone in the court of the law, no matter what race, background, or position that the person has.