Albert Barnes Commentary Psalms 119:118

"Thou hast set at nought all them that err from thy statutes; For their deceit is falsehood." — Psalms 119:118 (ASV)

Thou hast trodden down all them that err from thy statutes (Psalms 119:118) — Compare the notes at (Psalms 119:21). Rather, “You have made light of,” or “you despise.” The Hebrew word properly means to suspend in a balance; to weigh. Then it means to lift up lightly or easily; and then, to make light of; to treat with contempt; to regard anything as “light.” The Septuagint and Latin Vulgate render it, “You do despise.”

That is, God regards them as of no account, as a light substance of no value, as chaff which the wind carries away. Compare (Job 21:18); (Psalms 1:4); (Psalms 35:5); (Isaiah 17:13).

For their deceit is falsehood (Psalms 119:118) — This seems to be a truism, for deceit must imply falsehood. In the original, this is an emphatic way of declaring the whole thing to be false, as the Hebrew language often expresses emphasis by mere repetition — thus “pits, pits,” meaning many pits.

The psalmist first characterizes their conduct as deceitful—as that which cannot be relied on and which must fail in the end. He then speaks of this system on which they acted as altogether a “lie”—as that which is utterly “false.” This gives, as it were, a double emphasis to the statement, showing how utterly delusive and vain it must be.