The word of God, the Bible, is sufficient. It is the perfect standard of spiritual truth for life and faith. This is because the Bible is God's exhaled word. It reveals everything necessary for salvation and to glorify God. There is nothing lacking. There is nothing missing. Scripture is sufficient; it is enough. We do not need anything else. Scripture is sufficient for the believer to live and honor God. There is nothing more needed in the church.
Scripture is sufficient to: feed the sheep, call the lost, sanctify the believer, disciple the follower, heal the wounded, guide the wayward, encourage the disheartened, open the eyes of the blind, satisfy the thirsty, praise the Lord, strengthen the weak, combat the enemy, warn the offender, comfort the anguishing, give hope to the suffering, instruct the listening, and enrapture the faithful. Scripture is sufficient for preaching, teaching, evangelizing, and discipling- the four ministries of the body of Christ.
In fact, it is when people do not understand or believe that Scripture is sufficient, that trouble comes. What usually happens is that something else is added to the word of God (or key doctrines or teachings are removed or ignored). Someone adds their words or teachings to that of Scripture. Most cults and false teachers do this very thing. The sufficiency of Scripture guards against this tendency.
2 Timothy 3:15-17 teaches the sufficiency of Scripture. “[H]ow from childhood you have been acquainted with the sacred writings, which are able to make you wise for salvation through faith in Christ Jesus. 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 competent, equipped for every good work.”
Scripture is sufficient for salvation- “acquainted with the sacred writings, which are able to make you wise for salvation through faith in Christ Jesus.” It is sufficient to be our authority- “All Scripture is breathed out by God.” It is sufficient to profit believers- “and profitable for teaching, for reproof, for correction, and for training in righteousness.” And Scripture is sufficient to equip believers to do good works in order to glorify God- “that the man of God may be competent, equipped for every good work.”
That is not all. Scripture is sufficient to: sanctify (Jn. 17:17), aid believers in resisting temptations (Matt. 4:4), be blessed (Lk. 11:28), save without supernatural affirmation or miracles (Lk. 16:27-31), penetrate our deepest parts (Heb. 4:12), liberate and fulfill (Jms. 1:25), and cause growth and maturity (1Pet. 2:2). Scripture is sufficient for the discovery of everything a believer ought to think, do, believe, and know.
The sufficiency of Scripture warns us to never add anything to the Bible or hold other writings as its equal. Since the word of God is sufficient, we are not to believe anything about God or his salvation that is not found within its pages. Again, we have everything we need. We are to trust that the Lord has revealed and given us what is necessary.
The sufficiency of Scripture teaches us that nothing is sin that is not prohibited in the Bible explicitly by implication or by principle. This guards against legalism or the “I have to” attitude. We as Christians do not “have to” do anything, but we “get to.” We get to read the word, pray, go to church, etc. It is extremely easy to manufacture a list of rules and abide by them. It is also equally easy to measure others according to that list and look down on those who do not measure up to our standards. Often, these man-made lists are viewed as proof of holiness or godliness. Man's lists are not Scripture, nor are they a test of holiness.
Christians have certain freedoms in Christ. If something is not prohibited in Scripture, than believers can have freedom to enjoy that while exercising wisdom and discernment. For example, cards, movies, bingo, etc. are obviously not mentioned in Scripture. There are no principles within the Bible that teaches that these things are wrong. They can, however, be abused or sinful just like anything else. Notwithstanding, believers are not sinning by going to a movie or playing cards. Godly wisdom and discretion must be used, but Christians have freedom.
The sufficiency of Scripture also teaches that nothing is required of believers by God that is not found in the Bible explicitly, either by implication or by principle. If the word of God does not command it or suggest it, then believers do not have to do it- regardless of what others may say. The word of God is our sufficient authority, not the words of man.
Believers are reminded by the doctrine of the sufficiency of Scripture to be content with what God has revealed in his word. Beware of overemphasizing doctrinal or ethical teachings to an unscriptural level. Trust that the Lord has given us exactly what he willed and knew that we needed. We do not need the words or wisdom of man- we posses the very words of God!