The following quote by James Denney--a pastor and seminary professor of a century ago, who couldn't imagine a sermon that wasn't a declaration of the love of God--declares that there is a motivation in the love of God that is so life-giving that no other motivation is necessary.
“It is through the assurance, given to faith at the cross, that so far as doing the will of God is concerned, a new and living way has been found. It is not the law in its old legal form—the law of statutory injunctions and prohibitions—which is to generate goodness in the sinful man; it is the law glorified in the atonement. The whole inspiration of the Christian life lies here, and it is an inspiration, not a statutory requirement. Nothing is to count in the life of a Christian which does not come with perfect freedom from this source. This explains the extraordinary emphasis which St. Paul everywhere lays on liberty. Liberty is the correlative of responsibility; man must be perfectly free that the whole weight of his responsibilities may come upon him.” -The Death of Christ, by James Denney, pp.190-191
The whole inspiration of the Christian life lies here.
Do you agree with Denney that the whole inspiration of the Christian life lies in the cross and its transformative power? Are you persuaded that the law was honored and glorified in the atonement and nowhere else? When you think of Christ, do you think of the weightiness of the law and of Christ gladly carrying it all for you? Are you persuaded that in Christ you are perfectly free from all obligation to do good? Does even just hearing of that possibility make your heart sing and soar, or do you perhaps suspect and expect some laziness?
Let's get practical. Are you as a Christian bothered by your lack of motivation to do what is good? Are you bothered by such in other Christians? Is your solution to look at what is good for you and them to do and then to seek to do it? If so what is behind the motivation to seek to do it? This is the point of contention. A reason to act takes one of two general forms: either of obligation (have to or need to), or of gratitude for love or blessing received. You may declare that there is always a mixture of both. That likely is the human experience. But don't we all know intuitively that such is impure and akin to a business transaction? Business transactions are good but not in the place of a non-business personal interaction. We all may do this and do it often, but let's not pretend that God encourages it, as such isn't good. I suggest that the way to escape this polluted motivation is to take James Denney's advice and identity the problem as a lack of assurance in the power of the cross. Declare as true--and thank God often for it--that Christ in His death carried all your obligation to do what is good and that you are perfectly free, having no pressure of obligation. Denney is declaring that if you have any obligation to do good then your sense of responsibility to always do good will be diminished and impoverished. And that certainly isn't a good thing. If you are not convinced and think that you and others need at least a little pressure of obligation in order to be serious about doing what is good, then I have two questions for you. First, how is that going for you--I mean, compared to Christ are you obedient? And second, does God consider your imperfect performance as good?
I suggest that James Denney has clearly identified what God declares to be good and pure motivation--one that is untainted with human pride, competition, and failure. I also suggest that this motivation has sufficient force behind it to move me to proper action--done naturally and gladly. Jesus did say something like that: "He who forgiven much (and while perceiving it) loves much." It is crucial to notice that love in action isn't automatic, perception is necessary for it to flow naturally, freely, easily, and gladly. Lastly, I suggest that if Denney is correct here, then other sources of motivation are impure and thus not from God; they are worldly.