Albert Barnes Commentary Psalms 119:11

"Thy word have I laid up in my heart, That I might not sin against thee." — Psalms 119:11 (ASV)

Thy word have I hid in mine heart - Compare the notes at Psalms 37:31. The word rendered “hid” means properly to conceal, so that a thing may be secret, private, or inaccessible; then, to lay up in private, to treasure up, to hoard—as money or jewels—commonly “hidden” from public view (Job 20:26; Psalms 17:14).

Then it means to lay up in one’s heart, as a secret, inaccessible place; to hide one’s thoughts, purposes, or 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 - This means that it might protect me from sinning against you. The purpose is that I might be continually guided by its precepts, that I might be admonished of duty, and that I might be deterred from going astray.