Reading Alexander H. Stephens memoirs of the meeting between Confederate commissioners (including Stephens), Lincoln, and Seward, this is what he said Lincoln said on emancipation and the 13th amendment.

"I asked Mr. Lincoln what would be the status of that portion of the Slave population in the Confederate States, which had not then become free under his Proclamation; or in other words, what effect that Proclamation would have upon the entire Black population? Would it be held to emancipate the whole, or only those who had, at the time the war ended, become actually free under it? Mr. Lincoln said, that was a judicial question. How the Courts would decide it, he did not know, and could give no answer. His own opinion was, that as the Proclamation was a war measure, and would have effect only from its being an exercise of the war power, as soon as the war ceased, it would be inoperative for the future. It would be held to apply only to such slaves as had come under its operation while it was in active exercise. This was his individual opinion, but the Courts might decide the other way, and hold that it effectually emancipated all the slaves in the States to which it applied at the time. So far as he was concerned, he should leave it to the Courts to decide. He never would change or modify the terms of the Proclamation in the slightest particular. Mr. Seward said there were only about two hundred thousand slaves, who, up to that time, had come under the actual operation of the Proclamation, and who were then in the enjoyment of their freedom under it; so, if the war should then cease, the status of much the larger portion of the slaves would be subject to judicial construction. Mr. Lincoln sustained Mr. Seward as to the number of slaves who were then in the actual enjoyment of their freedom under the Proclamation. Mr. Seward also said, it might be proper to state to us, that Congress, a day or two before, had proposed a Constitutional Amendment for the immediate abolition of slavery throughlout the United States, which he produced and read to us from a newspaper. He said this was done as a war measure. If the war were then to cease, it would probably not be adopted by a number of States, sufficient to make it a part of the Constitution; but presented the case in such light as clearly showed his object to be, to impress upon the minds of the Commissioners that, if the war should not cease, this, as a war measure, would be adopted by a sufficient number of States to become a part of the Constitution, and without saying it in direct words, left the inference very clearly to be perceived by the Commissioners that his opinion was, if the Confederate States would then abandon the war, they could of themselves defeat this amendment, by voting it down as members of the Union. The whole number of States, it was said, being thirty-six, any ten of them could defeat this proposed amendment. I inquired how this matter could be adjusted, without some understanding as to what position the Confederate States would occupy towards the others, if they were then to abandon the war. Would they be admitted to representation in Congress? Mr. Lincoln very promptly replied, that his own individual opinion was, they ought to be. He also thought they would be; but he could not enter into any stipulation upon the subject. His own opinion was, that when the resistance ceased and the National Authority was recognized, the States would be immediately restored to their practical relations to the Union. This was a form of expression repeatedly used by him during the conversation, in speaking of the restoration of the Union....[Lincoln] Whatever may have been the views of your people before the war, they must be convinced now, that Slavery is doomed. It cannot last long in any event, and the best course, it seems to me, for your public men to pursue, would be to adopt such a policy as will avoid, as far as possible, the evils of immediate emancipation This would be my course, if I were in your place. Mr. Seward also indulged in remarks at considerable length on the progress of the Anti-Slavery sentiment of the country, and stated that what he had thought would require forty or fifty years of agitation to accomplish, would certainly be attained in a much shorter time. Judge Campbell inquired of Mr. Seward if he thought, that agitation upon the subject of the political relations between the two races would cease upon the emancipation of the Blacks-the point to which heretofore it had been entirely confined. Mr. Seward replied, perhaps not, or possibly not. Other matters were then talked over relating to the evils of immediate emancipation, if that policy should be pressed, especially the sufferings which would necessarily attend the old and the infirm, as well as the women and children, who were unable to support themselves."