Sanctification.

Herman Witsius has written:

Having thus previously explained these things, it will not be hard to infer, what we mean by Sanctification; namely, that real work of God, by which they, who are chosen, regenerated, and justified, are continually more and more transformed from the turpitude of sin, to the purity of the divine image.”

(Witsius, Herman. The Economy of the Covenants Between God and Man, Volume II, Kingsburg, CA: den Dulk Christian Foundation, 1990, p. 6)