What was Abraham lincolns 1858 warning that a house divided against itself cannot stand referred to sectional differences over what?

Abraham Lincoln's 1858 warning that "a house divided against itself cannot stand" referred to the deepening sectional differences in the United States, particularly over the issues of slavery and its expansion into new territories. He argued that the nation could not endure permanently half slave and half free; it would eventually have to become all one thing or all the other. This statement highlighted the growing tensions between the Northern states, which were increasingly anti-slavery, and the Southern states, which defended the institution of slavery.