If God had said he will forgive one sin, it would have been undeserved grace. But when he says he will pardon all but one, this is grace of the highest order. Nor is that one [unpardonable] sin otherwise but because the Saviour that should save them is rejected and put away.
We read of Jacob’s ladder. Christ is Jacob’s ladder that reaches up to Heaven, and he that refuses to go by this ladder will not, though using other means, get up so high. There is none other name given under heaven among men whereby we must be saved. There is also none other sacrifice for sin than his. He also, and he alone is the Mediator that reconciles men to God. And sinner, if you would be saved by him, his benefits are yours… even though you are a great and Jerusalem transgressor.
—John Bunyan, “The Jerusalem Sinner Saved”