Sanctification

Sanctification is an immediate work of the Spirit of God on the souls of believers, purifying and cleansing of their natures from the pollution and uncleanness of sin, renewing in them the image of God, and thereby enabling them from a spiritual and habitual principle of grace, to yield obedience unto God.

Or more briefly, it is the universal renovations of our natures by the Holy Spirit into the image of God, through Jesus Christ.

—John Owen, Triumph Over Temptation