“the precepts of the Lord are right, rejoicing the heart; the commandment of the Lord is pure, enlightening the eyes;” -Psalm 19:8
The precepts (piqqûd) and commandment (mitsvâh) seem to speak of the precise instructions and the authoritative orders, respectively, with which God addresses his people, Israel. Some suggest David has in mind the specific civic statutes by which God applies his Law to everyday life. Whether this is the case, or David is speaking more generally about the nature of God’s Law, it implies the righteousness and purity of God’s revealed jurisprudence is a source of delight and enlightenment.
Since man’s law in antiquity was often harsh and frequently unjust (e.g., Hammurabi’s code), God’s Law given to Israel through Moses, and which clearly delineates between good and evil, justice and injustice, and cultivates civic order and human flourishing, rejoiced the hearts of God’s people (Proverbs 29:2).
Further, the explication and application of God’s Law which showed how fallen human reason was from God’s pure reason was a primary source of human enlightenment. It showed in theory and practice what right and wrong looked like. Interestingly, a treatment of the practical implications of the Ten Commandments, for example, is astonishingly instructive and delightful when compared to modern jurisprudence.
Finally, it is this Law that God gave to humanity to be a guardian (i.e., a schoolmaster) to bring us to Christ (Galatians 3:24).