You will never know, or delight in, the will of God until His law is “within your heart.” The fact that that it’s written anywhere else has little to do with its application in your own life. It is not the “hearers” (or the readers) of the law who are justified, says Paul in Romans two, but the “doers.”
We used to sing a little chorus in Sunday School that said, “In a good place for a good purpose/ I will hide God’s Word in my heart.” (“Thy word have I hid in my heart, that I might not sin against God” Psl. 119:11). We may use this verse to encourage memorization of the Bible, but rote does not automatically translate into reality. I know the Ten Commandments, but it doesn’t always keep me from coveting; and I don’t know about you, but quoting Romans 8:28 hasn’t kept me from asking, “Why?” plenty of times. It’s the Word of God hidden—and housed—within our hearts that generates authenticity and much more.
By his own testimony, before his conversion, C.S. Lewis made the decision to make a study of the claims of God and the Bible; and as it will be with any truly honest questioner, he found those claims to be true. He had thought that simply finding the truth would be sufficient; but, alas, knowledge alone did not bring peace. In fact, it was just the opposite. He was convinced that becoming a Christian would lead to a life of joyless misery. But finally, he says, he reluctantly (his word) committed his heart and life to Jesus Christ for now and all eternity. It was then, when the law of God took root in his heart, that to his surprise (his word again), his soul, heart, and mind were all filled with …joy!
His word—and mine!