Moral Law
"One lesson and only one, history may be said to repeat with distinctness: that the world is built somehow on moral foundations; that, in the long run, it is well with the good; in the long run, it is ill with the wicket (sic). "
James A. Froude, Short Studies, Volume 1, page 22F
King is quoted the historian, James Froude.
I think Rev. King meant to write "....is ill with the wicked." .