Psalm 40:8 "I delight to do your will, O my God; your law is within my heart."

What was David's motive for obeying the law of God: duty or delight? Throughout the Psalms, we read of God's commands to keep his law, to obey it diligently. We also read of the psalmists' delight in obeying the law of God. The language of duty and delight emerges throughout Scripture, and there are few questions pertaining to the means of our sanctification that are as confounding as the question about our motive for obeying God.

As we observe in Psalm 40, David expresses his delight to do the will of God. He seems to answer the question that naturally follows this expression of delight, namely, Why do you delight to do the will of God?, with the rejoinder: "your law is within my heart." David was not coerced to keep the law of God but found it a delight to carry out God's will precisely because God had put his law in David's heart. Nevertheless, we do not get the impression that his delight in obeying the Law somehow eliminated his obligation, or duty, to obey the Law. For John Owen, the whole matter is more simple as he redirects our entire line of questioning to the work of Christ and our union with Christ.

According to Owen, a believer's motivation to obey the law is informed by Christ's mediatory work on our behalf. Owen writes:

"This renders all our moral obedience evangelical. For there is no duty of it, but we are obliged to perform it in faith through Christ, on the motives of the love of God in him, of the benefits of his mediation, and the grace we receive by him: whatever is otherwise done by us is not acceptable unto God" (John Owen A Declaration of the Glorious Mystery of the Person of Christ, God and Man [London: William Baynes, 1812], p. 180).

For Owen, the question of our motive for obedience cannot be reduced simply to the two options of duty and delight. Rather, he would argue, we need to come at the whole question of our motive for obedience from a different approach, namely, from Christ.

Christ's mediatory work, in his obedience, actively in fulfilling the righteous demands of God's law, and passively in his atoning work on the cross, is the ground of our motivation. We are motivated to obey because of the power of Gospel truth that has shone abroad in our hearts informing us, equipping us, and motivating us to follow Christ in his perfect obedience to the law.

The foundation of our obedience, then, is the love of a gracious God that has been poured out in our new hearts by the Holy Spirit whom he has given us. Question 90 of the Heidelberg Catechism asks, "What is the quickening of the new man?" Answer: "It is a sincere joy of heart in God, through Christ, and with love and delight to live according to the will of God in all good works." Positionally, who we are as new creatures in Christ informs what we do and why we do what we do. The juxtaposition we often establish between duty and delight as separate motives for doing the will of God is rightly seen a false dichotomy. Thus, we grasp what Matthew Henry drives at when he writes, "When the law of God is written in our hearts our duty will be our delight."

If we are Christ's, we have been given a new heart and, thus, cannot help but want to obey God. In Christ, we are new creatures who want to obey because we have been set free to obey the perfect law of liberty. As the children of God, we are motivated to do the will of God by the very fact that we are his in Christ. And even when we don't obey as our old flesh wars against the Spirit, we respond with obedient repentance unto life, being enabled more and more to die unto sin, and to live unto righteousness.

As we live unto righteousness by the work of God's free grace, being daily renewed in the whole man after the image of God, our motives are informed by a full range of resulting emotions that cause us to obey from our new hearts: our love of God, his love for us, his loving chastisement of us, our thankfulness to God, our joy in God, his joy in us, our comfort and peace from God, the holiness of God, our holiness in Christ from God, our duty to God, his promise to us, our delight in God, and our love for all that God has bestowed on us, including his most gracious law for us and our children.

In most simple terms, Sinclair Ferguson explains, "So what is the place of the Law in the life of the Christian? Simply this: We are no longer under the Law to be condemned by it, we are now "in-lawed" to it because of our betrothal to Christ! He has written the Law, and love for it, into our hearts!"