Although the U.S. Constitution (approved September 17, 1787) contains no direct references to slavery, it includes several indirect references to that "peculiar institution." The following are the references as well as translations of the legal language.
Article I, Section 2 . . . Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons. . . .
Translation: State representation and taxation will be based on the number of "free Persons" (whites) plus "three fifths of all other Persons" (blacks), implying that blacks are less than full human beings. This passage is generally referred to as the "three-fifths rule."
The passage was changed by Section 2 of the Fourteenth Amendment (ratified July 9, 1868): "Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State, excluding Indians not taxed."
Article I, Section 9. The Migration or Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred and eight, but a Tax or duty may be imposed on such Importation, not exceeding ten dollars for each Person.
Translation: The "Importation" of certain persons (the slave trade) could be stopped after 1808. After that date, Congress could place a tax on anyone brought into the United States as a slave. This passage had a horrific impact on enslaved Africans, because slave traders would sometimes dispose of their "cargo" to avoid paying taxes.
