Jamieson, Fausset and Brown on Psalms 19:7-9

7-9. The law is described by six names, epithets, and effects. It is a rule, God's testimony for the truth, His special and general prescription of duty, fear (as its cause) and judicial decision. It is distinct and certain, reliable, right, pure, holy, and true. Hence it revives those depressed by doubts, makes wise the unskilled (2Ti 3:15), rejoices the lover of truth, strengthens the desponding (Psa 13:4; 34:6), provides permanent principles of conduct, and by God's grace brings a rich reward.