The 1835 D&C says "it is not right that any man should be in bondage one to another."
Joseph Smith, "Section 97" Doctrine and Covenants (Kirtland: F. G. Williams & Co., 1835), 239
And let honorable men be appointed, even wise
men, and send them to purchase these lands; and every
church in the eastern countries when they are built up, if they
will hearken unto this counsel, they may buy lands and gather
together upon them, and in this way they may establish Zion.
There is even now already in store a sufficient; yea, even
abundance to redeem Zion, and establish her waste places no
more to be thrown down, were the churches, who call themselves
after my name willing to hearken to my voice. And,
again I say unto you, those who have been scattered by their
enemies, it is my will that they should continue to importune
for redress, and redemption, by the hands of those who are
placed as rulers, and are in authority over you, according to
the laws and constitution of the people which I have suffered
to be established, and should be maintained for the rights and
protection of all flesh, according to just and holy principles,
that every man may act in doctrine, and principle pertaining
to futurity, according to the moral agency which I have given
unto them that every man may be accountable for his own sins
in the day of judgment. Therefore it is not right that any
man should be in bondage one to another. And for this purpose
have I established the Constitution of this land, by the
hands of wise men whom I raised up unto this very purpose,
and redeemed the land by the shedding of blood.