What rule hath God given to direct us how we may glorify and enjoy him?

The word of God, which is contained in the Scriptures of the Old and New Testaments, is the only rule to direct us how we may glorify and enjoy him.[1]

Ephesians 2:20 (NASB)

having been built on the foundation of the apostles and prophets, Christ Jesus Himself being the corner stone,

2 Timothy 3:16-17 (NASB)

All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work.

The latin, “Sola Scriptura,” was the rallying cry of the Reformation. It would be Scripture alone by which Protestant churches would be organized, and the rule by which the followers of Jesus Christ would live out their lives. The Old Testament is the writings of the prophets and the New Testament is the writings of the apostles; Jesus Christ is the corner stone of both the Old Testament and the New Testament because he is the Word of God become flesh. (Jn. 1:1, 14) The Scriptures were held hostage by the medieval catholic church, and was freed for all the people to read in the protestant reformation. 

1 John 1:3 (NASB)

what we have seen and heard we proclaim to you also, so that you too may have fellowship with us; and indeed our fellowship is with the Father, and with His Son Jesus Christ.

The Scriptures came under attack in the post-reformation period. Then in the modern era skepticism, naturalism, and mysticism came to the forefront; however, can a sinful man, living in a sinful world, come to know and worship the Father God and the Son of God without the Scriptures? There is a natural revelation, but because of sin, man needs a special revelation from God, and it has come to us in the Scriptures, that we might know and have fellowship with the Father and the Son through reading and studying the Scriptures in both the Old and New Testament text.

[1] The Shorter Catechism, Question 2.