No, Robert E. Lee never said this. This is a mis-quote from an "interview" that a reverend named John Leyburn claimed to have had with Robert E. Lee in 1869, several years after the war was over, and a year before Lee's death.

John Leyburn had been born in Lexington, Virginia, and was a Presbyterian pastor. At the outbreak of the Civil War, Leyburn left his church and joined the South. He became Secretary of the Board of Publication for the newly-founded Southern Presbyterian Church, since the Presbyterian Church of the United States of America had become officially pro-abolitionist. (The two churches continue to be separate today.) After the war, Leyburn resettled in Baltimore, where he claimed to interview Lee.

An article by Leyburn was printed in 1885 in Century Illustrated magazine, so the quote itself is second-hand knowledge many years after the fact. Leyburn claimed to have asked if Lee had fought the war over the issue of slavery, and he said that Lee denied it. Leyburn claimed that Robert E. Lee told him:

"So far," said General Lee, "from engaging in a war to perpetuate slavery, I am rejoiced that slavery is abolished. I believe it will be greatly for the interests of the South. So fully am I satisified of this, as regards Virginia especially, that I would cheerfully have lost all I have lost by the war, and suffered all I have suffered, to have this objective obtained." This he said with much earnestness.

After expressing himself on this point, as well as others in which he felt that Northern writers were greatly misrepresenting the South, he looked at me and, with emphasis, said:

"Doctor, I think some of you gentlemen that use the pen should see that justice is done us."

So it would seem that this was in part an effort by Lee to resurrect his reputation after the fact. Or, it never happened, and it's something that Leyburn made up himself in order to resurrect Lee's reputation and promote Southern apologist sentiment.

There is a bit of truth to this view of Lee, however. In 1856, several years before the war, Robert E. Lee wrote a letter to his wife that explained some of his feelings on the subject of slavery, and this letter is used by most biographers as the cornerstone of Lee's personal views on slavery (1, 2, 3):

"There are few, I believe, in this enlightened age, who will not acknowledge that slavery as an institution is a moral and political evil. It is idle to expatiate on its disadvantages. I think it is a greater evil to the white than to the colored race. While my feelings are strongly enlisted in behalf of the latter, my sympathies are more deeply engaged for the former. The blacks are immeasurably better off here than in Africa, morally, physically, and socially. The painful discipline they are undergoing is necessary for their further instruction as a race, and will prepare them, I hope, for better things. How long their servitude may be necessary is known and ordered by a merciful Providence.

Their emancipation will sooner result from the mild and melting influences of Christianity than from the storm and tempest of fiery controversy. This influence, though slow, is sure. The doctrines and miracles of our Saviour have required nearly two thousand years to convert but a small portion of the human race, and even among Christian nations what gross errors still exist! While we see the course of the final abolition of human slavery is still onward, and give it the aid of our prayers, let us leave the progress as well as the results in the hands of Him who, chooses to work by slow influences, and with whom a thousand years are but as a single day."

In other words, though Robert E. Lee felt slavery was a "moral and political evil", he also felt it best to leave it in the hands of God to decide, and that slavery would end, eventually, on its own accord, even if that meant a thousand years hence. His letter goes on to say that the abolitionists should know that the way to end slavery is not to "excite angry feelings in the master" and that this would only make things worse. Lee's was not an unusual "moderate" point of view on slavery in the South in the 1850s.

Yet, even though Robert E. Lee may have felt slavery was morally and politically evil, he was not against perpetuating the institution himself. In 1856, his father-in-law, George W. P. Custis, died, and on his death bed, it was reported that he told a group of his slaves that he wanted them emancipated upon his death. But no white person was in the room, and Custis's will stated that they should be freed five years after he died.

This story reached the Washington D.C. correpsondent of the Boston Traveller newspaper, who printed an article about it on December 24, 1857, with the further claim that there were plans to sell some of the slaves down South before the emancipation date came.

Robert E. Lee responded by writing to the New York Times on January 8, 1858, denying that Custis had ever said such a thing, that the slaves would be free in five years' time according to the will, and that he had no plans to sell them "on South":

"What Mr. Custis is said to have stated to the Washington correspondent of the Boston Traveller, or to his assembled slaves, on his death bed is not known to any member of his family. But it is well known that during the brief days of his last illness, he was constantly attended by his daughter, grand-daughter, and niece, and faithfully visited by his physician and pastor. So rapid was the progress of his disease, after its symptoms became alarming, that there was no assembly of his servants, and he took leave of but one, who was present when he bade farewell to his family."

Was the Boston Traveller passing along false information or was Robert E. Lee telling the truth? It couldn't be proven in a court of law because "the testimony of negroes will not be taken in Court." So it wasn't until 1866 that the testimony of any of Custis's slaves was ever taken, and a former slave named Wesley Norris refuted Lee's version of events.

This had led Norris and several other slaves to try to escape in 1859, but they were caught:

"We were tied firmly to posts by a Mr. Gwin, our overseer, who was ordered by Gen. Lee to strip us to the waist and give us fifty lashes each, excepting my sister, who received but twenty."

So although Robert E. Lee professed a hatred for slavery before the war, and denied he engaged in the war over the issue of slavery after the war, he nonetheless was willing to participate and help preserve the institution both before and during the war. Though he freed some of his slaves before the war, he did not free the last of them until the war was over.

Lee's views on slavery have continued to be debated by biographers and historians. A century ago, the assessment by pro-Union authors was not kind. In a book about abolitionist John Brown, historian Franklin Benjamin Sanborn wrote of Lee's "lost cause" fight for slavery and printed the alleged Leyburn quote. He followed it with his own assessment of it:

"I print this in justice to a brave soldier; but his warfare was as much in defence of slavery as Hector's in defence of Helen, though the great Trojan did not approve of Paris as against Menelaus."

More recently, in discussing Lee's alleged Leyburn quote, historian Charles P. Roland put it:

If he actually made this statement, he doubtless exaggerated what he would have been willing to do in order to eliminate slavery, but there is compelling evidence that he was sincere in saying he was happy about its elimination (though not over the manner in which this occurred), and that he had not fought in order to preserve it.

Eric Foner, Civil War historian and professor at Columbia, put it succinctly by saying, "[Lee] was not a pro-slavery ideologue. But I think equally important is that, unlike some white southerners, he never spoke out against slavery."

Further Reading:

Robert E. Lee and the Southern Confederacy, 1807-1870 by Henry Alexander White, 1912

Lee Considered: General Robert E. Lee and Civil War History by Alan T. Nolan, 1996

Robert E. Lee: A Biography by Emory M. Thomas, 1997

The Making of Robert E. Lee by Michael Fellman, 2003

Reading the Man: A Portrait of Robert E. Lee Through His Private Letters by Elizabeth Brown Pryor and Robert E. Lee, 2007