Albert Barnes Commentary Psalms 119:158

"I beheld the treacherous, and was grieved, Because they observe not thy word." — Psalms 119:158 (ASV)

I beheld the transgressors - Those who wronged me; those who violated the law of God.

And was grieved - Or, “sickened.” The word used here means commonly to loathe, to nauseate, to sicken. (Ezekiel 16:47; Psalms 95:10). I was made sad, sorry, sick at heart. I did not look on them with anger; I did not desire to take revenge upon them; I did not return evil for evil. My heart was sad that people would do wrong; that they would expose themselves to such danger. See the notes at (Psalms 119:136).

Because they did not keep your word - Because they violated your law; because they were sinners.