Albert Barnes Commentary Psalms 119:151

"Thou art nigh, O Jehovah; And all thy commandments are truth." — Psalms 119:151 (ASV)

You are near, O Lord — God was present with him; he was ready to hear his cry; he was near to save him. Compare Psalms 145:18. The psalmist had the assurance, springing from deep feeling, and the conscious presence of God, which the people of God often have, that God is very near to them; that he is ready to hear them; that their prayers are answered; that they are in the presence of a heavenly Friend. Such are among the precious experiences of the life of a religious man.

And all your commandments are truth — All that you have ordained; all that you have promised. The psalmist felt this. He was experiencing the truth of what God had assured him of. Not a doubt came into his mind—for God was near him. This conviction that God is “near” us—this manifestation of God to the soul as a present God—is one of the most certain assurances to our own minds of the truth of religion, and of our acceptance with him.