This seems to me to contradict some of the things you have implied about Lincoln's attitude towards Slavery in your earlier posts. These were based on his statements in the Lincoln/Douglas debates and his one desperate attempt to divert the war by saying that if he could preserve the Union without freeing a single slave, he would do it.

Here he explicitly says that if God wills it, the war should "continue until all the wealth piled by the bondsman’s two hundred and fifty years of unrequited toil shall be sunk, and until every drop of blood drawn by the lash shall be paid by another drawn with the sword". That sounds like a man who would have fought for the idea of Forty acres and a Mule, if he had lived.