What specific connections between slavery and the war does lincoln make when he says, “if god wills that it continue until all the wealth piled by the bondman's two hundred and fifty years of unrequited toil shall be sunk, and until every drop of blood drawn with the lash shall be paid by another drawn with the sword . .” (lines 49–52)?

Lincoln is comparing the atrocities of both slavery and war. He references blood being taken by both the lash (in slavery) and the sword (in war). He is asking if the war must continue until it draws the same amount of blood that was drawn by slavery. He also asks if the war must continue until all development (that occurred as a result of slave labor) is destroyed by the war.