"Faith is the one great work Christians have to do in sanctification according to the principles of the gospel (John 6:29); it is the means of sanctification par excellence. . . .
Faith breaks all self-reliance and fastens on to God's promise. It allows the law to stand in all its grandeur and refuses to lower the moral ideal, but also refrains from any attempt, by observing it, to find life and peace; it seizes upon God's mercy and relies on the righteousness and holiness accomplished in Christ on behalf of humans. It fosters humility, dependence, and trust and grants comfort, peace, and joy through the Holy Spirit."
(--Herman Bavinck, Reformed Dogmatics 4:257)
“Because sanctification, like the whole of salvation, is the work of God, we are admonished, obliged, to a new obedience, and we are also qualified for it. He grants abundant grace not that we should instantly or suddenly be holy and continue to rest in this holiness, but that we should persevere in the struggle and remain standing. He hears our prayers but does it in accordance with the law and order which He has fixed for the spiritual life. Hence we are always of good course, for He who has begun a good work in us will finish it until the day of Jesus Christ. The believers can and they will become holy because in Christ they are holy”
(--Bavinck, Our Reasonable Faith, p. 502-3).