In order for the words of the Lord really to abide in us, it seems clear that we should commit as many of them to memory--not only in our minds, but in our hearts--as we possibly can. "Thy word have I hid in mine heart," the psalmist said, "that I might not sin against thee" (Psalm 119:11).
There are many promises of blessing to those who have God's Word in their hearts. "For it is a pleasant thing if thou keep them within thee; they shall withal be fitted in thy lips" (Proverbs 22:18). "My son, if thou wilt receive my words, and hide my commandments with thee; . . . Then shalt thou understand the fear of the Lord, and find the knowledge of God" (Proverbs 2:1, 5).
Both the apostle Paul and the apostle Peter have noted the importance of Scripture memorization. Paul says: "Let the word of Christ dwell in you richly in all wisdom; teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord" (Colossians 3:16).
Peter's exhortation is as follows: "This second epistle, beloved, I now write unto you; in both which I stir up your pure minds by way of remembrance: That ye may be mindful of the words which were spoken before by the holy prophets |i.e., the Old Testament Scriptures|, and of the commandment of us the apostles of the Lord and Saviour |i.e., the New Testament Scriptures|" (2 Peter 3:1-2). The words "be mindful" mean essentially "recall to mind."
Since the Scriptures cannot be recalled to mind unless they've first been installed in the mind, and since they cannot abide in our hearts unless we first hide them in our hearts, it is surely pleasing and honoring to God that we learn "by heart" as much of His Word as we can. HMM http://www.icr.org/article/6112/