Bonhoeffer: On hearing and doing the law.

A hearing which does not at the same instant become a doing becomes once again that "knowing" which gives rise to judgement and so leads to disruption of all action. If what is heard does not become doing, but if it becomes this "knowing", then, paradoxical as this may sound, it is already "forgotten" (James 1:25). No matter how long it may be stored up, reconsidered and elaborated as knowledge, it is forgotten as that which it essentially is, namely, as that which points solely and entirely towards action. The hearer of the word who is not at the same time the doer of the word thus inevitably falls victim to self-deception (James 1:22). Believing himself to know and to possess the word of God, he has, in fact, already lost it again, because he imagines that a man can possess the word of God for a single instant otherwise than in doing it.

From Ethics by Dietrich Bonhoeffer