I'm reading through R. D. Culver's Systematic Theology, and found this worth sharing:
Since God is holy, His will is holiness—perfect moral goodness—for every moral being. Lack of conformity to divine law, therefore, constitutes sin as sin. Its root is the very essence of uncongeniality of the creature’s fallen nature with the Creator’s perfectly holy nature. ‘Be ye holy, for I am holy’ is the permanent order of the created heaven and earth, but any man who glimpses that holiness becomes immediately aware he is not holy at all. Yet he knows he ought to be and must be.
[Culver, R. D. (2005). Systematic Theology: Biblical and Historical (p. 350). Ross-shire, UK: Mentor]