This is the quote/explanation I have been looking for! In trying to explain the concept of sin to people I've looked for a short explanation which best sums up the nature of sin. I've never been quite happy with the standard explanations of the nature of sin because they usually somehow make their way to the idea that sin is something you do.
In my overeagerness to counter that I have sometimes thought that sin is something you are, not that you do, but that's not right either. We "are" not sin - we are image bearers. So the definition of sin falls somewhere in between or outside of those two things and I think Oswald Chambers nails it here - this is from the October 5 reading in "My Utmost for His Highest."
The disposition of sin is not immorality and wrong-doing, but the disposition of selfrealization—I am my own god (italics mine). This disposition may work out in decorous morality or in indecorous immorality, but it has the one basis, my claim to my right to myself. When Our Lord faced men with all the forces of evil in them, and men who were clean living and moral and upright, He did not pay any attention to the moral degradation of.the one or to the moral attainment of the other; He looked at something we do not see, viz., the disposition.
Interestingly, in the rest of the reading for the day I think he is pretty weak on the concept of original sin, but I think he is right on in these words. I've always thought that one of the best bible verses for explaining the concept of sin is Luke 19:14:
19:14 But his citizens hated him and sent a delegation after him, saying, ‘We do not want this man to be king over us!’
In that light I think Chambers nails it.