I believe that you are wrong in that. Lincoln was a strong supporter of what would become the 13th Amendment ending slavery. He supported in the the Senate, was instrumental in having it added to the 1864 Republican platform, and pressed for the House to pass the Amendment when they convened in December 1864.
Some have suggested that. But we also know for certain that he was a strong supporter of the other 13th amendment perpetuating slavery forever. So strong a supporter was Lincoln that he in fact helped draft the language of it, lobbied intensely for it in Congress, whipped the votes for it in both the House and Senate, and publicly endorsed the thing in his Inaugural Address.
In his 1860 inaugural address, Lincoln said: "I have no purpose, directly or indirectly, to interfere with the institution of slavery in the states where it exists. I believe I have no lawful right to do so, and I have no inclination to do so."
Two years later, President Lincoln wrote: "My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it; and if I could save it by freeing some and leaving others alone I would also do that. What I do about slavery, and the colored race, I do because I believe it helps to save the Union (Letter to Horace Greeley, August 22, 1862)."
In 1858 Lincoln wrote: "I am not, nor ever have been, in favor of bringing about in any way the social and political equality of the white and black races. I am not, nor ever have been, in favor of making voters or jurors of Negroes, nor of qualifying them to hold office, nor to intermarry with white people. There is a physical difference between the white and black races, which I believe will forever forbid the two races living together on terms of social and political equality."