This is a letter I found which was written from John Wesley to William Wilberforce a week before Wesley died. Fantastic stuff:
Feb 24, 1791
My Dear Sir,
Unless the Divine power has raised you up to be as Athanasius contra mundum, I see not how you can go through your glorious enterprise, in opposing that execrable villany which is the scandal of religion, of England, and of human nature. Unless God has raised you up for this very thing, you will be worn out by the opposition of men and devils; but if God be for you who can be against you. Are all of them together stronger than God? Oh be not weary of well-doing. Go on in the name of God, and in the power of His might, till even American slavery, the vilest that ever saw the sun, shall vanish away before it. That He who has guided you from your youth up may continue to strengthen you in this and all things, is the prayer of,
Your affectionate servant,
Robert Isaac Wilberforce & Samuel Wilberforce, The Life of William Wilberforce vol. I (London, John Murray: 1838), p. 297.