The Bible’s answer
No, it does not teach the doctrine of ‘once saved, always saved.’ A person who has gained salvation by faith in Jesus Christ can lose that faith and the salvation that comes with it. The Bible says that maintaining faith requires great effort, a “hard fight.” (Jude 3, 5) Early Christians who had already accepted Christ were told: “Keep working out your own salvation with fear and trembling.”—Philippians 2:12.
Bible verses that disprove the teaching of ‘once saved, always saved’
The Bible warns against serious sins that will keep a person from entering God’s Kingdom. (1 Corinthians 6:9-11; Galatians 5:19-21) If salvation could not be lost, such warnings would be meaningless. Instead, the Bible shows that someone who has been saved can fall away by returning to a practice of serious sin. For example, Hebrews 10:26 states: “If we practice sin willfully after having received the accurate knowledge of the truth, there is no longer any sacrifice for sins left.”—Hebrews 6:4-6; 2 Peter 2:20-22.
Jesus emphasized the importance of maintaining faith by giving an illustration in which he likened himself to a vine and his followers to branches on that vine. Some of them would at one time demonstrate faith in him by their fruits, or actions, yet would later fail to do so and be “thrown out like a [fruitless] branch,” losing their salvation. (John 15:1-6) The apostle Paul used a similar illustration, saying that Christians who do not maintain their faith “will be lopped off.”—Romans 11:17-22.
Christians are commanded to “keep on the watch.” (Matthew 24:42; 25:13) Those who fall asleep spiritually, whether by practicing “works belonging to darkness” or by not fully performing the works that Jesus commanded, lose their salvation.—Romans 13:11-13; Revelation 3:1-3.
Many scriptures show that those who have been saved must still endure faithfully to the end. (Matthew 24:13; Hebrews 10:36; 12:2, 3; Revelation 2:10) First-century Christians expressed joy when they learned that fellow believers were enduring in their faith. (1 Thessalonians 1:2, 3; 3 John 3, 4) Does it seem reasonable that the Bible would stress faithful endurance if those who did not endure would be saved anyway?
Only when his death was imminent did the apostle Paul feel that his salvation was assured. (2 Timothy 4:6-8) Earlier in his life, he recognized that he could still miss out on salvation if he gave in to fleshly desires. He wrote: “I pummel my body and lead it as a slave, so that after I have preached to others, I myself should not become disapproved somehow.”—1 Corinthians 9:27; Philippians 3:12-14.