I have hid thy word in my heart. This psalm not being composed for the personal and peculiar use of the author only, we may therefore understand, that as frequently as David sets before us his own example, under this model he points out the course we ought to pursue. Here we are informed that we are well fortified against the stratagems of Satan when God's law is deeply seated in our hearts. For unless it have a fast and firm hold there, we will readily fall into sin. Among scholars, those whose knowledge is confined to books, if they have not the book always before them, readily discover their ignorance; in like manner, if we do not imbibe the doctrine of God, and are well acquainted with it, Satan will easily surprise and entangle us in his meshes. Our true safeguard, then, lies not in a slender knowledge of his law, or in a careless perusal of it, but in hiding it deeply in our hearts. Here we are reminded, that however men may be convinced of their own wisdom, they are yet destitute of all right judgment, except as far as they have God as their teacher.

Thy word have I hid in mine heart - Compare the notes at Psalm 37:31. The word rendered "hid" means properly to conceal, so that a thing may be secret, private, inaccessible; then, to lay up in private, to treasure up. to hoard - as money or jewels - commonly "hidden" from public view. Job 20:26; Psalm 17:14. Then it means to lay up in one's heart, as a secret, inaccessible place; to hide one's thoughts; purposes, designs; or to lay up knowledge or wisdom in the heart as a treasure, Job 10:13; Proverbs 2:1; Proverbs 7:1. The meaning here is, that he had "treasured" up the word of God, as the most valuable thing, in his heart; it was "there," though unseen; it constituted the secret power by which he was governed; it was permanently deposited there, as the most valuable of his treasures.
That I might not sin against thee - That it might protect me from sinning against thee. That I might be continually guided by its precepts; that I might be admonished of duty; that I might be deterred from going astray.

Thy word have I hid in my heart -
7. He must treasure up those portions of God's word in his mind and heart which speak against uncleanness of every kind; and that recommend purity, chastity, and holiness. The word of Christ should dwell richly in him. If God's word be only in his Bible, and not also in his heart, he may soon and easily be surprised into his besetting sin.

Thy word have I (b) hid in mine heart, that I might not sin against thee.
(b) If God's word is carved in our hearts, we will be more able to resist the assaults of Satan: and therefore the prophet desires God to instruct him daily more and more in it.

Thy word have I hid in mine heart,.... Not only heard and read it, but received it into his affections; mixed it with faith, laid it up in his mind and memory for future use; preserved it in his heart as a choice treasure, where it might dwell richly, and be of service to him on many occasions; and particularly be of the following use:
that I might not sin against thee; the word of God is a most powerful antidote against sin, when it has a place in the heart; not only the precepts of it forbid sin, but the promises of it influence and engage to purity of heart and life, and to the perfecting of holiness in the fear of the Lord; and all the doctrines of grace in it effectually teach the saints to deny all sin and worldly lusts, and to live a holy life and conversation; see 2-Corinthians 7:1.

Hid - I have laid it up in my mind like a choice treasure, to be ready upon all occasions to counsel, quicken or caution me.