Psalms 40:7-10

7. Then said I, Lo! I come. By the adverb then he intimates, that he had not been a good scholar, and capable of profiting by instruction, until God had opened his ears; but as soon as he had been instructed by the secret inspirations of the Spirit, he tells us, that then his heart was ready to yield a willing and cheerful obedience. Here true obedience is very properly distinguished from a constrained and slavish subjection. Whatever service, therefore, men may offer to God, it is vain and offensive in his sight, unless at the same time they offer themselves; and, moreover, this offering of one’s self is of no value unless it be done willingly. These words, Lo! I come, ought to be observed, and likewise the words, I have delighted to do thy will; for the Hebrew word חפצתי, chaphatsti, means, I was well pleased, or, I willingly condescended. Here David indicates his readiness to yield obedience, as well as the cordial affection of his heart and persevering resolution. His language implies, that he cordially preferred the service of God to every other desire and care, and had not only yielded a willing subjection, but also embraced the rule of a pious and holy life, with a fixed and steady purpose of adhering to it. This he confirms still further in the third clause of the verse, in which he says, that the Law of God was deeply fixed in the midst of his bowels It follows from this, first, that however beautiful and splendid the works of men may appear, yet unless they spring from the living root of the heart, they are nothing better than a mere pretense; and, secondly, that it is to no purpose that the feet, and hands, and eyes, are framed for keeping the Law, unless obedience begin at the heart. Moreover, it appears from other places of Scripture, that it is the peculiar office of the Holy Spirit to engrave the Law of God on our hearts. God, it is true, does not perform his work in us as if we were stones or stocks, drawing us to himself without the feeling or inward moving of our hearts towards him. But as there is in us naturally a will, which, however, is depraved by the corruption of our nature, so that it always inclines us to sin, God changes it for the better, and thus leads us cordially to seek after righteousness, to which our hearts were previously altogether averse. Hence arises that true freedom which we obtain when God frames our hearts, which before were in thraldom to sin, unto obedience to himself.

In the roll of the book As the Septuagint has made use of the word head instead of roll, some have been inclined to philosophise upon this clause with so much refinement of speculation, that they have exposed themselves to ridicule by their foolish and silly inventions. But the etymology of the word במגלת, bemegilath, is the same as the Latin word volumen, which we call a roll It is necessary to ascertain in what sense David claims peculiarly to himself what is common or alike to all men. Since the Law prescribes to all men the rule of a holy and upright life, it does not appear, it may be said, that what is here stated pertains to any one man or any set of men. I answer, that although the literal doctrine of the Law belongs to all men in common, yet as of itself it is dead, and only beats the air, God teaches his own people after another manner; and that, as the inward and effectual teaching of the Spirit is a treasure which belongs peculiarly to them, it is written of them only in the secret book of God, that they should fulfill his will. The voice of God, indeed, resounds throughout the whole world, so that all who do not obey it are rendered inexcusable; but it penetrates into the hearts of the godly alone, for whose salvation it is ordained. As a general, therefore, enrols the names of his soldiers, that he may know their exact number, and as a schoolmaster writes the names of his scholars in a scroll, so has God written the names of his children in the book of life, that he may retain them under the yoke of his own discipline.