For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
There are no outward signs that a person is a believer.
Those who have trusted Jesus alone apart from works are saved.
Romans 4:5-8. And Romans 3:26-28. Romans 11:6. Romans 6:23 For the wages of sin is death, but the GIFT of God is eternal life, through Jesus Christ our Lord.
Anyone who has accepted the free gift of eternal life by faith alone in Jesus finished work on the cross alone is saved.
Ephesians 1:13-14 Our guarantee of eternal life. Ephesians 4:30 And grieve not the Holy Spirit in whom ye are sealed unto the day of redemption.
Can you see the Holy Spirit in another person? No. Only God can. Whoever has believed is born again by the Spirit of God and is saved.
Second Timothy 2:19 Nevertheless, the foundation of God is sure, having this SEAL, Ephesians 1:13, The Lord knoweth them that are His.
We are saved by believing the gospel. Not by how we live or do not live. Man can do nothing to save himself, and once we are saved we can never be lost.
We can only be saved by what Jesus did for us. Romans 11:6.
Believers agree with John 3:16-18. Believers agree with Romans 1:16 For I am not ashamed of the gospel of Christ, for it is the POWER of God unto salvation to everyone that BELIEVETH, to the Jew first, and also to the Greek.
We are saved the second we trust Jesus as the only way of salvation. Nothing we do or do not do can save sinners.
So can we tell if a person is saved or not by the outward or the way they are living? No. We can only go by what they say, and they may have once believed and do not remember it or have departed from the faith. They are still saved.
Second Timothy 2:13 If we believe not, He abideth faithful, He can not deny HImself. His Holy Spirit that lives in all believers.
Since we are all sinners to a degree, First John 1:8, then you cannot tell one sinner from another sinner.
If they say they KNOW they are saved by the blood of Jesus that covers us from all sin, then you have to believe that person is saved by what they say. First John 5:13 These things have I written unto you that believe on the name of the Son of God, that ye may KNOW YE HAVE ETERNAL LIFE.
Anyone who has accepted Jesus free GIFT of eternal life is saved. John 6:47. John 6:40. John 10:28-29.
John 3:18. We all look alike. Those that have believed the gospel are saved. First Corinthians 15:1-4. Those that have not are not saved. The simplicity of the gospel is what saves sinners.
First Corinthians 1:18 For the preaching of the cross is to them that perish foolishness, but unto us who are saved it is the POWER of God.
First Corinthians 1:21 For after that, by the wisdom of God, the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.
Lots of people profess to be Christians, but their faith is not in Christ alone but in what they do or do not do.
Romans 6:23 For the wages of sin is death, but the GIFT of God is eternal life, through Jesus Christ our Lord.
The GIFT of God is eternal life. Once we accept the gift we have eternal life. A gift is paid in full by the giver. John 3:18 Believers can no longer be condemned to hell because they have believed on the name of the Son of God. John 1:12.
Since the GIFT of God is eternal life, then once we receive the gift we have eternal life. Since it is eternal it cannot be lost.
Hebrews 13:5 He will never leave us or forsake us. John 6:37. He will never cast us out. John 6:40 And this is the will of Him who sent me, that ALL that seeth the Son, and believeth on Him, may have everlasting life, and I will raise him up on the last day.
First John 2:2 Christ died for the sins of the whole world. So He died for my sins. Since He died for my sins I cannot go to hell because I have no sins to pay for. Since I cannot go to hell I have to go to heaven. Colossians 2:13. He has forgiven us all trespasses.
We are all sinners. Romans 3:23. Jesus paid the sin debt for us so we would not have to go to hell.