A proof text is usually defined as a quote taken out of context and misused to reach a conclusion that does not really fit what a broader reading would indicate was the true meaning. Yet, almost every scripture quoted in the gospels seems to be stretched somewhat and to have a major shift in meaning from what those who first heard it would have found. It seems as if all scripture is a proof text.
Which makes sense. When scripture comes into the world it is trapped by the limits of the language, the experiences and the context of the person recording it. By being recorded in mortal realms, by fallible humans with imperfect language, it becomes a proof text from what it was in its celestial context.
Scripture also comes intended to be used over and over again; to be reused to communicate to every person and generation, no matter how far removed from the original recording.
Thus scripture starts as a proof text by virtue of being captured or recorded, and is only freed and given true context as it comes to life outside of the original words and setting. As a result scripture only ceases to be a proof text as it comes into your life and is freed from its frozen state by finding the meaning it was intended to have for you.
In a way, scripture is not true until it becomes a proof text.
For a different approach to the same topic, see Wheatandtares.org on Thursday morning.