The Bible is necessary. General revelation, as discussed in a previous post, is not sufficient to reveal God or his plan of redemption. Scripture, therefore, is necessary for knowledge of the gospel and to know the will of God for maintaining spiritual life. General revelation does not reveal the sins of men or the person and work of Christ. It cannot tell man how to live or glorify God. Something else is needed. That something else is the written word of God, the scriptures.
The Bible is necessary for salvation. The gospel must be heard. In order to believe in Christ he must be proclaimed and heard. “For 'everyone who calls on the name of the Lord will be saved.' How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? And how are they to preach unless they are sent? As it is written, 'How beautiful are the feet of those who preach the good news!' But they have not all obeyed the gospel. For Isaiah says, 'Lord, who has believed what he has heard from us?' So faith comes from hearing, and hearing through the word of Christ. (Rom. 10:13-17) “Whoever believes in him is not condemned, but whoever does not believe is condemned already, because he has not believed in the name of the only Son of God.” (Jn. 3:18)
The Bible reveals that Christ alone is the way of salvation. “Jesus said to him, 'I am the way, and the truth, and the life. No one comes to the Father except through me.'” (Jn. 14:6) “And there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved.” (Acts 4:12)
It is in Scripture that we learn that Christ is the only mediator between God and man. “For there is one God, and there is one mediator between God and men, the man Christ Jesus, who gave himself as a ransom for all, which is the testimony given at the proper time.” (1Tim. 2:5-6)
Salvation is through the word of God. “For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek.” (Rom. 1:16) “I write these things to you who believe in the name of the Son of God that you may know that you have eternal life.” (1Jn. 5:13)
The word of God teaches us that Christ died according to the scriptures, that he was buried, and that he rose again according to the scriptures. “Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, and by which you are being saved, if you hold fast to the word I preached to you-unless you believed in vain. For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures...” (1Cor. 15:1-4)
The word of the cross is the power of God for salvation. “For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God.” (1Cor. 1:18)
John wrote his gospel in order for people to know that Jesus is the Christ and have life in his name. “Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.” (Jn. 20:30-31)
Christ crucified is the message that must be proclaimed. “For Jews demand signs and Greeks seek wisdom, but we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God.” (1Cor. 1:22-24)
The scriptures reveal that Christ was to suffer and rise from the dead, and that repentance be proclaimed in his name throughout the world. “Then he said to them, 'These are my words that I spoke to you while I was still with you, that everything 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 said to them, 'Thus it is written, that the Christ should suffer and on the third day rise from the dead, and that repentance and forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem.'” (Lk. 24:44-47)
Many more passages could be referenced, but these should suffice to demonstrate that the Bible is necessary for salvation. The word of God must be preached, taught, heard, learned, believed, and obeyed.
The Bible is also necessary in order to know the will of God. It is the will of God to trust him and not lean on one's own understanding. “Trust in the LORD with all your heart, and do not lean on your own understanding.” (Prov. 3:5)
It is God's will that believers: rejoice always, pray without ceasing, give thanks in everything, not quench the Spirit and despise prophetic utterances, examine everything, and abstain from evil. “Rejoice always, pray without ceasing, give thanks in all circumstances; for this is the will of God in Christ Jesus for you. Do not quench the Spirit. Do not despise prophecies, but test everything; hold fast what is good. Abstain from every form of evil.” (1Thess. 5:16-22)
God wills for us to be imitators of him and to walk in love. “Therefore be imitators of God, as beloved children. And walk in love, as Christ loved us and gave himself up for us, a fragrant offering and sacrifice to God.” (Eph. 5:1-2)
It is the will of God to put on his armor. “Finally, be strong in the Lord and in the strength of his might. Put on the whole armor of God, that you may be able to stand against the schemes of the devil. For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand firm. Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, and, as shoes for your feet, having put on the readiness given by the gospel of peace. In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; and take the helmet of salvation, and the sword of the Spirit, which is the word of God.” (Eph. 6:10-17)
Elders and deacons are to be qualified according to the revealed will of God. “The saying is trustworthy: If anyone aspires to the office of overseer, he desires a noble task. Therefore an overseer must be above reproach, the husband of one wife, sober-minded, self-controlled, respectable, hospitable, able to teach, not a drunkard, not violent but gentle, not quarrelsome, not a lover of money. He must manage his own household well, with all dignity keeping his children submissive, for if someone does not know how to manage his own household, how will he care for God's church? He must not be a recent convert, or he may become puffed up with conceit and fall into the condemnation of the devil. Moreover, he must be well thought of by outsiders, so that he may not fall into disgrace, into a snare of the devil. Deacons likewise must be dignified, not double-tongued, not addicted to much wine, not greedy for dishonest gain. They must hold the mystery of the faith with a clear conscience. And let them also be tested first; then let them serve as deacons if they prove themselves blameless. Their wives likewise must be dignified, not slanderers, but sober-minded, faithful in all things. Let deacons each be the husband of one wife, managing their children and their own households well. For those who serve well as deacons gain a good standing for themselves and also great confidence in the faith that is in Christ Jesus.” (1Tim. 3:1-13)
It is the will of God for Jews and Greeks to repent of sin and trust Christ. “I did not shrink from declaring to you anything that was profitable, and teaching you in public and from house to house, testifying both to Jews and to Greeks of repentance toward God and of faith in our Lord Jesus Christ.” (Acts 20:20-21)
God's will is for believers to be doers of the word and not merely hearers. “But be doers of the word, and not hearers only, deceiving yourselves.” (Jms. 1:22)
God's will is for believers to submit to authority. “Be subject for the Lord's sake to every human institution, whether it be to the emperor as supreme, or to governors as sent by him to punish those who do evil and to praise those who do good. For this is the will of God, that by doing good you should put to silence the ignorance of foolish people.” (1Pet. 2:13-15)
God wills for believers to guard themselves from idols. “ Little children, keep yourselves from idols.” (1Jn. 5:21)
Examples could be multiplied, but these are sufficient to show that we need the word of God in order to know his will. How are we to live lives that are glorifying to God and benefit others if we do not have his will recorded in the Bible? The word of God is necessary. So, read the Bible. It is necessary for your salvation as well as your sanctification; for your growth in godliness as well as your knowledge of the will of God.