This was the title of a speech delivered to the Illinois Republican State Convention by Abraham Lincoln on June 17, 1858. Lincoln was accepting the nomination as Republican candidate for a seat in the United States Senate. He would go on to challenge Democrat Stephen Douglas for the seat, and they would engage in the famed Lincoln-Douglas Debates.
Lincoln's point was that the Union could not endure with half of the States allowing slavery and half opposing it. "I do not expect the Union to be dissolved", Lincoln said, "but I do expect it will cease to be divided. It will become all one thing, or all the other." Mr. Lincoln did not, in 1858, expect that this would be accomplished under his presidency via the bloodsoaked years of the American Civil War. Rather, he thought it would happen legislatively, and via the unification of public opinion behind one viewpoint or the other.
Factors such as the Dred Scott case had stirred up passions about slavery like never before. The upcoming admittance of Kansas into the Union raised the question of whether it should be a slave or free state. Lincoln, as we know, held an anti-slavery position, though at this time not as strong a position as the war would eventually force on him.
Lincoln was indeed quoting the New Testament of the Bible: Matthew 12:25 and/or Mark 3:25.