Article 1, Section 9, Clause 1

Document 12

James Madison, Federalist, no. 42, 281--82

It were doubtless to be wished that the power of prohibiting the importation of slaves, had not been postponed until the year 1808, or rather that it had been suffered to have immediate operation. But it is not difficult to account either for this restriction on the general government, or for the manner in which the whole clause is expressed. It ought to be considered as a great point gained in favor of humanity, that a period of twenty years may terminate for ever within these States, a traffic which has so long and so loudly upbraided the barbarism of modern policy; that within that period it will receive a considerable discouragement from the foederal Government, and may be totally abolished by a concurrence of the few States which continue the unnatural traffic, in the prohibitory example which has been given by so great a majority of the Union. Happy would it be for the unfortunate Africans, if an equal prospect lay before them, of being redeemed from the oppressions of their European brethren! Attempts have been made to pervert this clause into an objection against the Constitution, by representing it on one side as a criminal toleration of an illicit practice, and on another, as calculated to prevent voluntary and beneficial emigrations from Europe to America. I mention these misconstructions, not with a view to give them an answer, for they deserve none; but as specimens of the manner and spirit in which some have thought fit to conduct their opposition to the proposed government.

The Founders' Constitution
Volume 3, Article 1, Section 9, Clause 1, Document 12
http://press-pubs.uchicago.edu/founders/documents/a1_9_1s12.html
The University of Chicago Press

Hamilton, Alexander; Madison, James; and Jay, John. The Federalist. Edited by Jacob E. Cooke. Middletown, Conn.: Wesleyan University Press, 1961.