The truth is that so long as we hold both sides of the proposition together they contain nothing inconsistent with orthodoxy, but as soon as one is divorced from the other, it is bound to prove a stumbling-block. "Only those who believe obey" is what we say to that part of a believer's soul which obeys, and "only those who obey believe" is what we say to that part of the soul of the obedient which believes. If the first half of the proposition stands alone, the believer is exposed to the danger of cheap grace, which is another word for damnation. If the second half stands alone, the believer is exposed to the danger of salvation through works, which is also another word for damnation.
-- Dietrich Bonhoeffer (1906-1945) in The Cost of Discipleship