(NOTE: Some of the themes of these articles may not be appropriate for young readers. Please keep that in mind when sharing this information).
It is written:
“If you think you are a prophet or that you have a spiritual gift, you should understand that what I am writing to you is the Lord’s command.” (1 Corinthians 14:37)
Just as the Old Testament claimed to be the Word of God to mankind, so also does the New Testament. This may be seen in several ways.
First, Jesus’ Apostles had a very special authority that no one else in the church has ever been honored to have. The authority of the Apostles may be seen from the word “apostle” itself.
“We saw in Chapter Four that the principle of apostolicity was central to the idea of a canon, and that it stems from the earliest days of the Christian community-indeed from the lifetime of Jesus himself. He appointed the Twelve to be his apostles, his shelichim, a word with very special meaning in Judaism. It meant a representative equipped with the full powers of his principal…“…It is interesting to note that the Jewish shaliach (apostle) could not hand on his commission to anyone else; it was for him alone…There was something unique and unrepeatable about their position. They were the guarantors of the continuity between the incarnate Jesus who walked the streets of Palestine and the glorified Jesus whom the church worshipped.” (Dr. Michael Green, The Books The Church Suppressed: Fiction And Truth In The Da Vinci Code, 84-84; Grand Rapids, Michigan; Monarch Books; emphasis added)
Jesus gave His Apostles His full authority to bind and loose on Earth what had been bound and loosed in Heaven (Matthew 16:19; 18:18).
Second, the actions and writings of the Apostles make it clear that they understood their writings (i.e., the New Testament Scriptures) to be inspired and authoritative.
“The Apostles asserted their authority. The apostles were well aware of their God-given authority. They were also well aware their teaching was from the Holy Spirit. Peter begins both letters with a reminder of his apostleship (1 Pet 1:1; 2 Pet. 1:1). He meekly asserts his right to impose his letter upon the church: “I who am… a witness of the sufferings of Christ” (1 Pet. 5:1). He argues for the divine origin of his message by reminding his followers that what they heard was preached “by the Holy Spirit sent from heaven” (1 Pet. 1:12). John also humbly attaches his apostolic authority to his Gospel with the words: “This is the disciple who testifies to these things and who wrote them down; we know that his testimony is true.” (Jn. 21:24) John knew he was passing along divine revelation concerning the Word of Life (1 Jn. 1:1-4). Paul opens many of his letters with a reminder of his God-ordained apostleship. Since he was not of the Twelve but received his apostleship later he seemed to always have to defend it. He is especially forced to throw his weight around to the Galatians and Corinthians. He told the latter, “What I am writing to you is the Lord’s command” (1 Cor. 14:37). To the former he said anything that contradicted his teaching must be ignored (v. 38)—anyone preaching another Gospel was to be accursed (Gal. 1:8, 9). In 1 Thes. 2:13 he makes the remarkable claim that to receive his teaching was to receive words from God….The apostles imposed their writings. Since the apostles were aware of their authoritative office it is reasonable to think that they intended to write books that would guide the church under that authority….Imposition can be seen in the commands that letters be circulated among the churches, even read publically in worship meetings (1 Thess. 5:27; Col. 4:16; Rev. 1:3)…Imposition is more subtle in other letters, yet it can still be seen. It was already mentioned that Peter wrote to “the pilgrims of the Dispersion” scattered broadly throughout five different regions (1 Pet. 1:1). James also wrote “to the twelve tribes which are scattered abroad” (Jam. 1:1). These are not the words of apostles writing to individual churches. It is reasonable to think that the apostles intended their letters to be widely distributed (i.e. imposed throughout regions)….The best and earliest example of apostolic imposition comes from the Bible itself. In Acts 15 we read that letters were written containing the decision of the apostles and elders at the close of the first Jerusalem Council (v. 23). Their decision was just not verbally imposed upon the church (v. 27) but circulated through written letters (v. 20, 23).  This set a clear precedence from the beginning. A written letter from an apostle (or apostles) was just as authoritative as if the commands were given in person by an apostle. To receive a written letter from an apostle was equal to a visit (cf. 3 John 13–14). Furthermore, spreading info this way was very useful. Written letters helped when making a trip in person was not possible (cf. 2 Thessalonians 2:2). It also helped reach a wider audience more quickly with an important message. Thus the apostles imposed their authority via written communication.” (Norman Geisler & Shawn Nelson, Evidence Of An Early New Testament Canon, 255-294 (Kindle Edition); Matthews, NC; Bastion Books)
Thus, the Old and New Testaments claim to be the inspired Word of God to mankind.
Yet just because a person or document claims to be speaking the Word of God does not mean that they are. I learned a personal lesson in this many years ago. A woman who showed up at my door had a very interesting story. When I answered the door, I asked her if I could help her. She said, “I need a bus ticket to Detroit.” I said, “Of course you do! But what does that have to do with me?” She responded, “GOD told me you would give me that ticket.”
OH NO HE DIDN’T!
So, the question remains: can we be certain that the Bible is the Word of God?