Let thy hand be to succor me. As he had devoted himself to the doctrine of the law, David requests that the hand of God may be stretched forth for his aid. Farther, by these words he declares, that those who yield themselves to God to be governed by His word have continually need of His help. The more sincerely any individual studies to be a good man, so much the more numerous are the ways in which Satan troubles him, and so much the more are the enemies multiplied who molest him on all sides. But when God sees those who once embraced the truth of his word remaining steadfast in their resolution, he is so much the more inclined to aid them. By the word choose in the second clause, the Psalmist has expressed that nothing had hindered him from devoting himself to the law of God. No man will apply this mind to the love of the law without a great struggle, since the thoughts of every man are drawn away to a variety of objects, by the depraved affections of the flesh. This choosing then spoken of shows that it is not through ignorance or an inconsiderate zeal that the children of God desire above all things heavenly doctrine; but as they partake of the flexibility or pliancy of mind common to men, and feel the various impulses of the flesh, they purposely subdue their minds to the obedience of God.

Let thine hand help me - Do thou help me - the hand being that by which we accomplish anything.
For I have chosen that precepts - I have chosen them as my comforters and my guide. I have resolved to obey them, and I pray that thou wilt help me to accomplish the purpose of my heart.

Let thine hand help me - Exert thy power in my defense.

Let thine hand help me,.... Let thine hand of power help me against mine enemies, and deliver me from them; and let thine hand of providence and grace communicate to me, and supply me with and help me to everything needful for me, for body and soul; for time and eternity, all grace here, and glory hereafter; let thy right hand help me on in my way, hold and uphold me, keep and preserve me safe to heaven and happiness;
for I have chosen thy precepts; not only the good part, which shall not be taken away, and the way of truth, Psalm 119:30; but even the commandments of God, which he preferred to the commandments of men, and choose rather to obey the one than the other; having a most ardent affection for them, an high esteem of them, and a strong attachment to them; see Psalm 119:127.

(Compare Psalm 119:77, Psalm 119:81, Psalm 119:92).
I have chosen--in preference to all other objects of delight.