Albert Barnes Commentary Psalms 119:125

"I am thy servant; give me understanding, That I may know thy testimonies." — Psalms 119:125 (ASV)

I am thy servant - See the notes at Psalms 116:16.

Give me understanding, that I may know thy testimonies - Since I am your servant, instruct me in the knowledge of your will. As I desire to obey you, show me what will be acceptable obedience, or what you do require in order to acceptable service. This is a prayer of piety. A man who sincerely desires to obey God will make it a first point to ascertain what is his will, or what will constitute true obedience.