Comfort of Assurance not found in works but in Christ alone...

Some Christians claim that part of the believer's assurance of salvation is to be found in 

the evidences of his obedience. The basis for that assertion, I've been told, is

found in the WCF 18 - Of the Assurance of Grace and Salvation. Frankly I don't find it. And I would posit that the measure of our obedience is ever changing, never perfect, and sometimes, due to sin, outright missing. Yet, I would say that our obedience nonetheless can to a degree help strengthen the assurance of our salvation inasmuch as we see even our imperfect obedience as 'fruits and evidences of a true and lively faith' (WCF 16.2) in Christ alone. Let's take a brief look.

WCF 18
Paragraph #1 describes who it is that may find assurance of salvation in this life. It is the true believer. Assurance is promised to those who 'truly believe in the Lord Jesus, and love him in sincerity, endeavoring to walk in all good conscience before him...' Endeavoring to obey the Lord is a characteristic of a true believer, but obedience itself is not here mentioned as a source or part of the ground of the believer's assurance.

Paragraph #2 states that the certainty of our salvation is 'an infallible assurance of faith founded upon the divine truth of the promises of salvation, the inward evidence of those graces unto which these promises are made, the testimony of the Spirit of adoption witnessing with our spirits that we are the children of God, which Spirit is the earnest of our inheritance, whereby we are sealed to the day of redemption'. Our obedience is a work that we do and should hardly be included with the 'inward evidence of those graces unto which these promises are made' which seems to point to those graces such as forgiveness of sins, a new heart and right-will, and the gift of the Holy Spirit that come to a believer through faith in Christ.

Paragraph #3 makes note that one may by justified by faith before such a time as he comes to an assurance of his salvation. But such assurance comes to all believers in due time as they diligently partake of the ordinary means of grace. Obedience is here listed as one of the 'proper fruits of this assurance' not a cause or source.

Paragraph #4 teaches that assurance can waver due to negligence of partaking of the means of grace, falling into sin and temptation, or a season in which God seems removed and far off. Yet this wavering doesn't extinguish the new birth in Christ and 'by the operation of the Spirit, this assurance may, in due time, be revived'.

Concerning this assurance of salvation, John Colquhoun makes an important point. Of believers he writes, 'Their graces themselves are imperfect, and therefore that assurance of sense, which arises from the perception of them, must be imperfect likewise'...

"Although the sight of his evidences of grace, is indeed pleasant to a holy man; yet the sight of Christ in the offer and promise, should be much more delightful to him. Unbelief and a legal spirit, will dispose a man always to look for something in himself, as his ground of comfort; but a holy faith, will have to do with none but Christ. Nothing is such a delight to the Lord Jesus; because nothing honours him so much, as direct and unsuspecting confidence in him, for salvation. Whereas, looking to him, or looking upon him, through one's own graces and frames, reflects much dishonour upon him. The man, who so looks upon him, is like one who sees the sun reflected by water; which appears to move or waver, as much as the surface of the water does."

John Colquhoun, A Treatise on Spiritual Comfort