It is becoming increasingly common today for people to ask if the Bible is necessary for Christianity. Now, if all you mean is, "can someone be saved without reading or even having access to a Bible," then the answer is, of course, that they can. When the gospel reaches a new tribe even though there is no Bible in their language or when underground churches live and die in faithfulness to Jesus in persecuted lands where they have no access to even a single copy of the Bible, these people are still Christians. Their faith is still Christianity. However, the gospel they have believed in is still traceable back to the Scriptures. The Bible has preserved the gospel, verifies the gospel, and is the infallible authority of the people of that gospel. So yes, the Bible is necessary for Christianity even though there are Christians who live in situations where they cannot have Bibles.
Typically, however, people who ask this question are not talking about the extreme circumstances of unreached mission fields or severe systematic persecution. What they mean is something more like, "Can't I disbelieve most of what the Bible says and still be a Christian as long as I love Jesus?" To which I must respond, "you can't love Jesus while disbelieving most of what the Bible says." Jesus Himself said:
"If they do not listen to Moses and the Prophets, they will not be persuaded even if someone rises from the dead," (Luke 16:31).
The resurrection of Jesus Christ is absolutely central and non-negotiable to true Christianity, but even the resurrection alone cannot establish Christianity. All kinds of false religions believe that Jesus rose from the dead and yet do not believe the gospel. If someone refuses to accept what God has revealed or twists the words of Scripture to their own liking, they can turn the resurrection of Jesus into whatever they want. The apostle Paul, reminding the Corinthians of the message he first preached to them, said:
"For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, and that He was buried, and that He was raised on the third day according to the Scriptures, and that He appeared to Cephas, then to the twelve," (1 Corinthians 15:3-5).
The gospel Paul received, preached, and expected the Corinthians to believe was not merely that Christ died for our sins, but that He did so according to the Scriptures. It was not simply that Christ rose from the dead, but that he arose according to the Scriptures. Indeed, Paul warns the Corinthians "not to exceed what is written," (1 Corinthians 4:6). Paul elsewhere says of his preaching:
"Having obtained help from God, I stand to this day testifying both to small and great, stating nothing but what the Prophets and Moses said was going to take place," (Acts 26:22).
And Paul wrote to the church at Rome that he is:
"set apart for the gospel of God, which He promised beforehand through His prophets in the holy Scriptures," (Romans 1:1-2).
The message of Jesus death, burial, resurrection, and future return only make proper sense in light of the witness of Scripture that defines for us what they mean and how we are to live in light of them. It is by the Scriptures that we know and understand the gospel. It is through the Bible that God has chosen to preserve this truth and carry it forth to all nations:
"Now to Him who is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery which has been kept secret for long ages past, but now is manifested, and by the Scriptures of the prophets, according to the commandment of the eternal God, has been made known to all the nations, leading to obedience of faith," (Romans 16:25-26).
After Jesus had died and risen, He confronted a group of doubting disciples, saying:
"O foolish men and slow of heart to believe in all that the prophets have spoken!" (Luke 24:25).
And as He went on to commission the Apostles to carry the gospel forward, He told them:
"'These are My words which I spoke to you while I was still with you, that all things which are written about Me in the Law of Moses and the Prophets and the Psalms must be fulfilled.' Then He opened their minds to understand the Scriptures, and He said to them, 'Thus it is written, that the Christ would suffer and rise again from the dead the third day, and that repentance for forgiveness of sins would be proclaimed in His name to all the nations, beginning from Jerusalem,'" (Luke 24:44-47).
The truth of the Scriptures is foundational to the gospel. It is also foundational to the Christian life. Paul wrote to the Roman Christians:
"For whatever was written in earlier times was written for our instruction, so that through perseverance and the encouragement of the Scriptures we might have hope," (Romans 15:4).
And to Timothy, regarding the practice of the churches:
"Until I come, give attention to the public reading of Scripture, to exhortation and teaching," (1 Timothy 4:12-14).
He also explained plainly that:
"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," (2 Timothy 3:16-17).
So yes, the Bible is absolutely foundational to Christianity. The gospel rests on its truth, and it is vital to the healthy growth and nurturing of the mature Christian life.