Q. 3. What do the Scriptures principally teach?
A. The Scriptures principally teach, what man is to believe concerning God,(e) and what duty God requires of man.(f)
(e) Gen 1:1; John 5:39; John 20:31; Rom 10:17; 2 Tim 3:15
(f) Deut 10:12-13; Josh 1:8; Ps 119:105; Mic 6:8; 2 Tim 3:16-17
(e1) John 5:39 You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me, (f1) Micah 6:8 He has told you, O man, what is good; and what does the Lord require of you but to do justice, and to love kindness, and to walk humbly with your God? (f2) 2 Timothy 3:16-17 All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work.
The Bible is a big book. It is actually 66 different books, spanning over 1500 years, written by over 40 different authors, penned upon 3 different continents, and in three different languages. These 66 different books were preserved by God and bound together in the one book we call the Bible. So what is the book about?
The third answer in our catechism answers the question of what the Scriptures principally teach. The Scriptures principally teach, what man is to believe concerning God, and what duty God requires of man.
Without the Scriptures, we are simply left to ourselves to try and determine what God is like, and what he requires of us. If you ask people what they believe about God, most will have some sort of opinion. But which opinions are true, and which are false? What standard do we use to compare each opinion against? Our own human reason?
The standard we are to compare all truth claims to is the Bible. It is the one trustworthy source which teaches us what we are to believe concerning God, and what duty he requires of us.