Albert Barnes Commentary Psalms 119:165

"Great peace have they that love thy law; And they have no occasion of stumbling." — Psalms 119:165 (ASV)

Great peace have they—See the notes on (Isaiah 26:3); compare with the notes on (Philippians 4:6–7). They have great calmness of mind. They are not troubled and anxious. They believe and feel that all things are well-ordered by you, and will be conducted to the best result. They, therefore, calmly leave all with you. As a matter of fact, the friends of God have peace and calmness in their minds, even amidst the troubles, the disappointments, and the reverses of life. The love of God is the best—the only—way to secure permanent peace in the soul.

Which love thy law—It is the love of law, and the belief that the law of God is in accordance with justice, that gives peace to their minds. God’s government is a government of law, and therefore it is loved.

And nothing shall offend them—Margin, "They shall have no stumbling-block." Hebrew, "And to them no stumbling," or stumbling-block. See the notes on (Matthew 5:29–30); (Matthew 18:6); (Matthew 16:23); (1 Peter 2:8); and (James 2:10). The meaning here is that they would not fall into sin; they would be kept safe; they would be preserved from the power of temptation. The meaning is not, as it would seem to be in our version, that nothing would pain, grieve, or irritate them; but, as above, that as long as they were obedient to the law, and disposed to obey it, they would be safe from the power of temptation.