Charles H. Spurgeon on Psalms 65:3

Iniquities prevail against me. There are two ways in which iniquities may prevail against the Christian —the first is in the growing sense of his guilt, the second is in the power of their acting. This prevalence cannot be entire, for sin shall not have dominion over them; but it may be occasional and partial. There are two ways, according to Scripture, in which God purges our transgressions; and they always go together. The one is by pardoning mercy. Thus David prays: "Purge me with hyssop, and I shall be clean." Thus the blood of Jesus Christ cleanseth us from all sin. The other is by sanctifying grace: "I will sprinkle clean water upon you, and ye shall be clean." And this is as much the work of God as the former. He subdues our iniquities as well as forgives them. William Jay.