Professing rationally to a written creed, theology or doctrine does not make one a Christian.
What does make one a Christian? Or, what does make one a believer, who also, at the same time, is a true disciple and follower of Christ?
According to the Bible the following is needed (in bold) for that:
One must be born again.
John 3. Jesus answered and said to him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.” “Truly, truly, I say to you, unless one is born of water and the Spirit he cannot enter into the kingdom of God. “That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. Do not be amazed that I said to you, ‘You must be born again.’ No one has ascended into heaven, but He who descended from heaven: the Son of Man. “As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up; so that whoever believes will in Him have eternal life. “For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life. “For God did not send the Son into the world to judge the world, but that the world might be saved through Him. “He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God. One must believe.
That means believing in Him with one’s whole heart. What else does it say? It does mean that one realizes one is totally doomed and one should believe and accept the sacrifice of Jesus. Repentance is totally part of it. One must repent. One should realize, like the people bitten by snakes in the desert, who would otherwise die when not looking in faith for rescue at the copper serpent that Moses had lifted up. In other words one should realize the problem of sin and of having commited sins and being guilty of it. One must realize that he is standing before a holy and just God.
That makes sense, because without that realization one would not be very eager to take the ‘cure’. But upon realizing it, one will be very grateful and very glad and eager to accept it with both hands. One should turn around and turn away from sin and a sinful life and accept Jesus as savior and Lord and from then on obediently follow Him.
Matthew 4:17. “From that time on Jesus began to preach, “Repent, for the kingdom of heaven has come near.”
Matthew 1:15. “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
Luke 5:32. “I have not come to call the righteous but sinners to repentance.”
Luke 13:3. “No, I tell you; but unless you repent, you will all likewise perish.”
Giving public witness, with the mouth, is also important and part of it.
“If you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved; for with the heart a person believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation.
Luke 12: 8,9.“And I say to you, everyone who confesses Me before men, the Son of Man will confess him also before the angels of God; but he who denies Me before men will be denied before the angels of God.”
What belongs to the former statement about confession has also to do with this.
One must be baptized (based on personal faith/conversion).
Mark 16:16. “He who has believed and has been baptized shall be saved; but he who has disbelieved shall be condemned.
What else?
Romans 8:9. “If anyone does not have the Spirit of Christ, he does not belong to Him.”
One must have the Holy Spirit living within, otherwise one is not a Christian.
When does someone receive the Holy Spirit?
Ephesians 1: 13. “In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise, who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory.”
In other words: the moment one starts to believe, that is when one has converted and repented and accepts and believes in Jesus as his personal savior, one, at that very moment receives the Holy Spirit in his heart.
One should be certain of salvation and of being a child of God after having converted and receiving the Holy Spirit.
Romans 8:16. “The Spirit Himself testifies with our spirit that we are children of God”.
Galatians 4: 6. “Because you are sons, God has sent forth the Spirit of His Son into our hearts, crying, “Abba! Father!”
1 John 5:13. “These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life.”
We should have love and love one another.
1 John 4. “Beloved, let us love one another, because love is from God; everyone who loves is born of God and knows God. Whoever does not love does not know God, for God is love.”
John 13: 34,35. “A new commandment I give to you, that you love one another, even as I have loved you, that you also love one another. By this all men will know that you are My disciples, if you have love for one another.”
Believing in the resurrection and ascension to heaven. 1 Corinthians 15:14. “If Christ has not been raised, our preaching is useless and so is your faith.” 1 Peter 3: 21-22. “Corresponding to that, baptism now saves you—not the removal of dirt from the flesh, but an appeal to God for a good conscience—through the resurrection of Jesus Christ, who is at the right hand of God, having gone into heaven, after angels and authorities and powers had been subjected to Him.”
Believe in a real Adam (as described in Genesis 1) and believe in Christ. 1 Corinthians 15:21. “For since death came through a man, the resurrection of the dead comes also through a man. For as in Adam all die, so in Christ all will be made alive.” 1 Corinthians 15:45. “So it is written: “The first man Adam became a living being”; the last Adam, a life-giving spirit.” 1 Timothy 2: 13. “For Adam was formed first, then Eve. And it was not Adam who was deceived, but the woman being deceived, fell into transgression.” See also Romans 5: 12-21. Genesis is confirmed from the New Testament as having literally happened. Denying (a literal and historical) Adam is basically denying Christ and (the necessity for) His atoning work.
We should bear fruit (see Galatians 5) and do the will of the Father in heaven.
Matthew 7: 15-23. “Every tree that does not bear good fruit is cut down and thrown into the fire. “So then, you will know them by their fruits. “Not everyone who says to Me, ‘Lord, Lord,’ will enter the kingdom of heaven, but he who does the will of My Father who is in heaven will enter. “Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ “And then I will declare to them, ‘I never knew you; depart from Me, you who practice lawlessness.'
1 John 2. “By this we know that we have come to know Him, if we keep His commandments. The one who says, “I have come to know Him,” and does not keep His commandments, is a liar, and the truth is not in him; but whoever keeps His word, in him the love of God has truly been perfected. By this we know that we are in Him: the one who says he abides in Him ought himself to walk in the same manner as He walked.
We should take up our cross and follow Him.
Matthew 16:24. “Then Jesus said to His disciples, “If anyone wishes to come after Me, he must deny himself, and take up his cross and follow Me. “For whoever wishes to save his life will lose it; but whoever loses his life for My sake will find it.”
Matthew 10:38. “And he who
does not take his cross and follow after Me is not worthy of
Me.”
Luke 14:27. “And whoever does not carry his
cross and follow Me cannot be My disciple.”
In summary, according to the Bible one is a Christian if:
One is born again.
One believes with the heart and has accepted Jesus Christ as Lord and Savior.
One has repented and converted (It involves acknowledging one's wrongdoing, feeling regret or remorse for it, and making a conscious decision to turn away from that wrongdoing and turning to Christ Jesus for salvation and fully trusting in Him and His work). One is fully aware of being a sinner and personally needing salvation, being in a lost state, and then gratefully believing and accepting the sacrifice of Jesus' atoning work on the cross.
One confesses his faith with his mouth.
One has been baptized upon one’s faith (or one should be baptized).
One has the Holy Spirit living within.
One is certain of salvation, trusting what the Bible says about it.
One has love for others.
One must believe in the resurrection and ascension.
One must believe in a real 1st Adam (Genesis) and a real Fall by man, in order to be able to fully believe in the 2nd ‘Adam’, Christ Jesus. That means believing in creation as described in Genesis 1 and 2 as having literally taken place. The Bible, including the NT and the gospels totally confirm it. The Bible gives no reason to read Genesis differently. No, it only confirms it. Jesus also confirms it (see also here and here).
One bears fruit and does the will of the Father.
One takes up his cross and follows Him.
Now, taking all that into account, do you consider yourself to be a Christian?
If not, what is lacking?