I have inclined my heart to perform thy statutes. In this verse he describes the right observance of the law, which consists in Our cheerfully and heartily preparing ourselves for doing what the law commands. Slavish and constrained obedience differs little from rebellion. The prophet, therefore, in order briefly to define what it is to serve God, asserts, that he applied not only his hands, eyes, or feet, to the keeping of the law, but that he began with the affection of the heart. Instead of the verb incline, the verb extend might with propriety be employed; but I am inclined to rest in the more generally received interpretation, which is, that he devoted himself with sincere affection of heart to the observance of the law. This inclination of the heart is oppose to the wandering lusts which rise up against God, and drag us any where rather than incline us to a virtuous life. The attempt of the Papists to defend from this passage their doctrine of free will is mere trifling. They infer from the words of the prophet, that it is in the power of man to bend his own heart in whatever way he pleases. But the answer is easy. The prophet does not here boast of what he had done by his own strength, for he now repeats the very same word which he had employed before, when he said, Incline my heart to these testimonies. If that prayer was not feigned, he doubtless acknowledged by it that it was the peculiar work of the Holy Spirit to incline and frame our hearts to God. But it is no new thing for that to be ascribed to us which God works in us: Paul's statement to this effect is very plain, "It is God who worketh in you, both to will and to do of his good pleasures" (Philippians 2:13.) When the prophet says of himself that he inclined his heart, he does not separate his own endeavor from the grace of the Holy Spirit, by whose inspiration he has previously declared that the whole was done. At the same time, he distinguishes the constancy of his pious affection from the transient favor of others. Thus, that he might not fail in the midst of his course, or even go backward, he affirms that he had resolved to continue in the same course during the whole of his life. The word qv, ekeb, to the end, in my opinion, is added to the word lvlm, leolam, for ever, by way of exposition; and to show us that he struggled manfully against all obstacles and difficulties, that they might not break his constancy; for no man perseveres in the service of God without arduous exertions. Some take the word as denoting a reward; [1] but this seems too foreign to the design of the passage.

Footnotes

1 - Thus, in the Arabic, it is, "on account of an eternal reward;" that is, the reward of grace promised to all the faithful. According to this view, the Psalmist would have a respect to the end and reward of faith and holy obedience. See Hebrews 11:26; 1-Peter 1:8, 9. As, however, the Psalmist, like all true believers, did not embrace and obey the law of God, only or chiefly from the hope of reward, but was chiefly attracted to obedience by love to God, and the intrinsic excellence of the law, others prefer reading "the reward is eternal."

I have inclined mine heart - The Hebrew word means properly "to stretch out"; "to extend" - as the hand. Exodus 8:6, Exodus 8:17. Then it means to incline, to bow, to depress. Here the idea is, that he had "given" that "direction" to the inclinations of his heart; he had resolved or purposed. He refers to an act of choice on his part, meaning that he had preferred this course, or that he had made this a solemn intention. Though every right inclination of the human heart is to be traced to the divine agency, yet it is also true that man is active in religion - or that his own mind resolves, chooses, and prefers - and that true religion is the actual choice or preference of all who serve God aright. See the notes at Psalm 119:59.
To perform thy statutes alway - Margin, as in Hebrew, "to do." He meant to do the will of God. He intended to do this constantly; even forever. No man can be a truly pious man who has any disposition, or any purpose, "ever" to turn away from the service of God.
Even unto the end - See Psalm 119:33. To the end of life; to the end of all things.

I have inclined mine heart - I used the power God gave me, and turned to his testimonies with all mine heart. When we work with God, we can do all things.

I have inclined mine heart to perform thy statutes alway,.... He had prayed to God to incline his heart to them, Psalm 119:36; and by the grace of God his heart was inclined to obedience to them; and nothing but that can incline the heart, which is naturally averse unto them: the carnal mind is not subject to the law of God, nor can it be, until it is made so by the grace of God, Romans 8:7; and by this the psalmist had prevailed upon his heart to keep the statutes of the Lord, and do them, and that continually; for a good man is desirous of being steadfast and immovable, always abounding in the work of the Lord;
even unto the end; the end of life, as long as he lived. The Septuagint and Vulgate Latin version render it, "for a recompence"; and the Arabic version, "for an eternal recompence"; but the Ethiopic version the reverse, "not for a recompence", or benefit: which latter is the truth, though neither of them a right version; for the statutes are to be kept, not for the sake of a recompence of reward, but from love to God, and; in duty to him, without any mercenary views; though the word does sometimes signify "a reward", and may be rendered here, "for ever there is a reward" (i); as there is "in", though not "for", keeping the commands; see Psalm 19:11.
(i) "in aeternum est retributio", Clarius.