John Owen on Self Cleansing from Sin is Impossible.

John Owen addresses directly the people who think they can cleanse themselves from sin by their own efforts. According to scripture we are too filthy and too weak to accomplish the task. External law and forces cannot do it. We need to be cleansed from the inside out.

We are unable of ourselves, without the special assistance of the Holy Spirit, to free ourselves from this pollution[the effects of sin]. It is true, it is frequently prescribed to us as our duty. We are commanded to wash ourselves, to cleanse ourselves from sin, and the like, but these expressions do not imply a power in ourselves to perform what is so required; but they teach us, that whatever God works in us in a way of grace, he prescribes to us in a way of duty; and though he does it in us, yet he also does it by us; so that the same work is an act of his Spirit and of our wills as actuated thereby. We are not able by an endeavours of our own, to cleanse ourselves from this defilement. 'If I wash myself with snow-water' saith Job, 'and make my hands ever so clean, yet shalt thou plunge me in the ditch, and my own clothes shall make me to be abhorred' (Job 9:29). Means may be used whereby an appearance of cleansing may be made, but when things come to be tried, in the sight of God, all will be found filthy and unclean, 'In vain', says the prophet, 'shalt thou take to thyself soap and much nitre; you shalt not be purged' (Jer. 2:22). The most probable means of cleansing, and the the most effectual in our judgement, however multiplied, shall fail in this case. Some speak much of washing away their sins by the tears of repentance; by repentance, as prescribed in the Scripture, is of another nature, and assigned to another end: men's tears are but 'soap and nitre', which will not produce the effect intended. The institutions of the law were of themselves insufficient for this purpose; they purified the unclean legally, and as to the flesh (Heb. 9:13); of themselves they could go no further, only they signified that whereby sin was really cleansed. The real stain is too deep to be removed by any outward ordinances, and therefore God, as it were rejecting them all, promised to open another fountain for that purpose (Zech. 13:1).

John Owen has another chapter on how the filth of sin is purged by the Spirit and blood of Christ. The introduction to the chapter reveals his argument.

The purification of believers from the defilement of sin, is assigned in Scripture to various causes--to the Holy Spirit, as the efficient cause; to the blood of Christ, as the procuring cause; and, to faith and affliction, as the instrumental causes.

The Holy Spirit is the craftsman who is making the sanctification happen. The blood of Christ is the price of our redemption. Faith and affliction are the tools the Holy Spirit is using to cleanse us from our sin.