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 Psalm 119:27, rendered there, "Make me to understand."

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

With my whole heart - I will not trifle with my God, I will not divide my affections with the world; God shall have all.

Give me understanding, and I shall keep thy law,.... A spiritual understanding; an understanding of the law, the perfection, purity, holiness, and spirituality of it; an understanding of the Gospel, and of Christ and the things of Christ; from whom grace and strength are to be had for the due observance of the law, as in his hands; which understanding must be given, and is a gift of pure, free, rich grace, to such who have it; though they cannot keep the law perfectly, as no mere man can, yet will keep it spiritually, from a principle of love and gratitude, and with a view to the glory of God and Christ, 1 John 5:20;

yea, I shall observe it with my whole heart; not only externally, and to be seen of men, and get applause from them; but doing the will of God from the heart, and with a good will and heartily, as to the Lord, and not to men; with a sincere affection for him, and with a single eye to his glory, Ephesians 6:6.

Give me understanding, and I shall keep thy law; yea, I shall observe it with my whole {b} heart.

(b) Not only in outward conversation, but also with inward affection.

119:33-40 Teach me thy statutes, not the mere words, but the way of applying them to myself. God, by his Spirit, gives a right understanding. But the Spirit of revelation in the word will not suffice, unless we have the Spirit of wisdom in the heart. God puts his Spirit within us, causing us to walk in his statutes. The sin here prayed against is covetousness. Those that would have the love of God rooted in them, must get the love of the world rooted out; for the friendship of the world is enmity with God. Quicken me in thy way; to redeem time, and to do every duty with liveliness of spirit. Beholding vanity deadens us, and slackens our pace; a traveller must not stand gazing upon every object that presents itself to his view. The promises of God's word greatly relate to the preservation of the true believer. When Satan has drawn a child of God into worldly compliances, he will reproach him with the falls into which he led him. Victory must come from the cross of Christ. When we enjoy the sweetness of God's precepts, it will make us long for more acquaintance with them. And where God has wrought to will, he will work to do.