Pilgrim basically summed up what the Westminster Confession has to say about Santification-

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I. They, who are once effectually called, and regenerated, having a new heart, and a new spirit created in them, are further sanctified, really and personally, through the virtue of Christ's death and resurrection,[1] by His Word and Spirit dwelling in them:[2] the dominion of the whole body of sin is destroyed,[3] and the several lusts thereof are more and more weakened and mortified;[4] and they more and more quickened and strengthened in all saving graces,[5] to the practice of true holiness, without which no man shall see the Lord.[6]

II. This sanctification is throughout, in the whole man;[7] yet imperfect in this life, there abiding still some remnants of corruption in every part;[8] whence arises a continual and irreconcilable war, the flesh lusting against the Spirit, and the Spirit against the flesh.[9]

III. In which war, although the remaining corruption, for a time, may much prevail;[10] yet, through the continual supply of strength from the sanctifying Spirit of Christ, the regenerate part does overcome;[11] and so, the saints grow in grace,[12] perfecting holiness in the fear of God.[13]

The mercy of God is necessary not only when a person repents, but even to lead him to repent, Augustine