"There, but for the grace of God, go I" customarily is attributed to John Bradford, as from his place of confinement in the Tower of London he watched some prisoners being led away to execution.
If we ponder this statement, it can be seen that the term "grace," as used here, is not only referring to forgiveness. Reverend Bradford eventually was burned at the stake.
I think there is a deeper meaning, having to do with Divine destiny. Why would God favor John Bradford with the success he had had throughout his life, coming from a "financially stable" home. The prisoners he was observing probably came from among poor people and were caught in a crim