The law of the LORD is perfect, reviving the soul; the testimony of the LORD is sure, making wise the simple; the precepts of the LORD are right, rejoicing the heart; the commandment of the LORD is pure, enlightening the eyes. –Psalm 19:7-8
2 Timothy 3:16 tells us that every bit of Scripture is profitable for teaching, reproof, correction, and for training in righteousness. These words describe what it means that the law of the Lord is perfect reviving the soul.
The word revive means to turn or restore. The picture here is of a soul that has been led astray for a time, but now desperately needs to turn back to Christ for restoration. Our memory verse instructs us that it is preciously the Law of the Lord which turns back the soul. It is perfect to bring this revival.