I have shown that slavery is wicked—wicked, in that it violates the great law of liberty, written on every human heart—wicked, in that it violates the first command of the decalogue—wicked, in that it fosters the most disgusting licentiousness—wicked, in that it mars and defaces the image of God by cruel and barbarous inflictions—wicked, in that it contravenes the laws of eternal justice, and tramples in the dust all the humane and heavenly precepts of the New Testament.
Inhumanity of Slavery. Extract from A Lecture on Slavery, at Rochester. December 8, 1850 - My Bondage and My Freedom (1855)