Our obedience is either the ground (the basis), the instrument (the means), or the evidence (the fruit) of our salvation. The Reformed doctrine is the latter. It is the case that believers will be progressively sanctified by the work of the Holy Spirit, through the due use of ordinary means, and that progressive sanctity will produce obedience in conformity to God’s holy law. That sanctity and concomitant and consequent obedience, however, is no part of the ground or instrument of our final salvation or acceptance with God.
[…] There is one ground of justification: Christ’s whole, perfect obedience credited to believers and received through faith defined as resting, receiving, leaning upon, trusting in Christ and his finished work. The new life wrought in us by the Spirit necessarily produces sanctity, and sanctity results in obedience and good works. The putting to death of the old man and the making alive of the new is a struggle. As a consequence of Christ’s gracious salvation of his people, they (we) owe him utter thankful obedience, which the Spirit is graciously producing in us, but that obedience never becomes any part of the instrument through which we are accepted with God or finally saved from the wrath to come. Read the full article by R. Scott Clark.