So shall I keep thy law continually,.... Which denotes not the perfection of keeping the law, but the constancy of it: the psalmist was persuaded, that so long as he had the word of truth in his mouth, and the judgments of God in his view, he should be diligent and constant in the discharge of his duty, which these directed and encouraged him unto; for ever and ever; in this life and that to come; when the law of God will be kept, and his will done perfectly by the saints, as it now is by the angels in heaven; or this may be connected with the law of God; which law is for ever and ever, being of eternal duration and obligation. The whole may be understood of the law of faith, or doctrine of the Gospel, and be rendered, "so shall I observe thy doctrine continually"; contained in the word of truth; which doctrine is for ever and ever, it is the everlasting Gospel.