Albert Barnes Commentary Psalms 119:34

"Give me understanding, and I shall keep thy law; Yea, I shall observe it with my whole heart." — Psalms 119:34 (ASV)

Give me understanding, and I shall keep thy law - Give me right views of it, of its nature and obligation. It is not a prayer that God would give him the faculty of understanding or intelligence; but that he would enable him to take just views of the law. The word is the same as in (Psalms 119:27), rendered there, Make me to understand.

Yea, I shall observe it with my whole heart - See (Psalms 119:2). I will keep it with undivided affections; I will make it the sole guide of my life.