David's conscience here witnesses for him,

I.That his practices were good. 1. He loved God's testimonies, he loved them exceedingly. Our love to the word of God must be a superlative love (we must love it better than the wealth and pleasure of this world), and it must be a victorious love, such as will subdue and mortify our lusts and extirpate carnal affections. 2. He kept them, his soul kept them. Bodily exercise profits little in religion; we must make heart-work of it or we make nothing of it. The soul must be sanctified and renewed, and delivered into the mould of the word; the soul must be employed in glorifying God, for he will be worshipped in the spirit. We must keep both the precepts and the testimonies, the commands of God by our obedience to them and his promises by our reliance on them.

II.That he was governed herein by a good principle: "Therefore I have kept thy precepts, because by faith I have seen thy eye always upon me; all my ways are before thee; thou knowest every step I take and strictly observest all I say and do. Thou dost see and accept all that I say and do well; thou dost see and art displeased with all I say and do amiss." Note, The consideration of this, that God's eye is upon us at all times, should make us very careful in every thing to keep his commandments, Gen 17:1.

My tongue shall speak of thy word,.... Of the word of God in general; of the truth of it, which he knew by certain experience; of the purity of it, tending to promote holiness of heart and life; of the power and efficacy of it, enlightening his mind, and working effectually in him; of the profit of it, to his learning, to his instruction, comfort, and refreshment; of the preciousness of it, being of more worth than thousands of gold and silver; and of the pleasantness of it, being sweeter than the honey or honeycomb, and more to be esteemed than one's necessary food; and of the promises of it in particular, of the worth and value of them, of their suitableness and use, and of the faithful fulfilment of them; and of the doctrines of the word, especially those which relate to the grace of God, and salvation by the Messiah; and also of the precepts of the word, as follows:

for all thy commandments are righteousness; not only righteous, but righteousness itself, being strictly just and equitable in the highest sense; and not only some of them, but all of them; see Psa 119:128. Aben Ezra's paraphrase of the words is,

"I will teach the children of men thy word, that they may know that thy commandments are righteousness;''

which is not amiss: and to the same sense is Kimchi's note, who observes, that author of the Masorah interprets it of praise; as if he had said, My tongue shall praise thy word, because all of it is righteousness.