However, this is the proper work of the law, to discover sin in the guilt of it, to awake and humble the soul for it, to be a glass to represent sin in its colours; and if thou deniest to deal with it on this account, it is not through faith, but through the hardness of thy heart and the deceitfulness of sin.
This is a door that too many professors have gone out at unto open apostasy. Such a deliverance from the law they have pretended, as that they would consult its guidance and direction no more; they would measure their sin by it no more. By little and little this principle hath insensibly, from the notion of it, proceeded to influence their practical understandings, and, having taken possession there, hath turned the will and affections loose to all manner of abominations.
By such ways, I say, then, as these, persuade thy conscience to hearken diligently to what the law speaks, in the name of the Lord, unto thee about thy lust and corruption. Oh! if thy ears be open, it will speak with a voice that shall make thee tremble, that shall cast thee to the ground, and fill thee with astonishment. If ever thou wilt mortify thy corruptions, thou must tie up thy conscience to the law, shut it from all shifts and exceptions, until it owns its guilt with a clear and thorough apprehension; so that thence, as David speaks, thy “iniquity may ever be before thee.”
– John Owen –
from The Mortification of Sin in Believers, volume 6 of Works, pages 57-58