Smith was against slavery on moral and economic grounds. The "invisible hand" in societies which allow slavery, operates in such a way that increases in the wealth of the rich, leads to increased misery for the poor free citizens as well as for the slaves themselves. It seems that the beneficial workings of the "invisible hand" are dependent upon commercial societies which arc not based upon the institution of slavery.
Pack, Spencer J., "Slavery, Adam Smith’s Economic Vision and the Invisible Hand" (1996). Economics Faculty Publications. 26.
The views expressed in this paper are solely those of the author.