Matthew 13:18 “Hear, then, the parable of the farmer. 19 When anyone hears the word of the Kingdom, and doesn’t understand it, the evil one comes, and snatches away that which has been sown in his heart. This is what was sown by the roadside. 20 What was sown on the rocky places, this is he who hears the word, and immediately with joy receives it; 21 yet he has no root in himself, but endures for a while. When oppression or persecution arises because of the word, immediately he stumbles. 22 What was sown among the thorns, this is he who hears the word, but the cares of this age and the deceitfulness of riches choke the word, and he becomes unfruitful. 23 What was sown on the good ground, this is he who hears the word, and understands it, who most certainly bears fruit, and produces, some one hundred times as much, some sixty, and some thirty.” (Scripture quotations from the World English Bible, public domain)
Matthew 7:16 By their fruits you will know them. Do you gather grapes from thorns, or figs from thistles? 17 Even so, every good tree produces good fruit; but the corrupt tree produces evil fruit. 18 A good tree can’t produce evil fruit, neither can a corrupt tree produce good fruit. 19 Every tree that doesn’t grow good fruit is cut down, and thrown into the fire. 20 Therefore by their fruits you will know them. 21 Not everyone who says to me, ‘Lord, Lord,’ will enter into the Kingdom of Heaven; but he who does the will of my Father who is in heaven. 22 Many will tell me in that day, ‘Lord, Lord, didn’t we prophesy in your name, in your name cast out demons, and in your name do many mighty works?’ 23 Then I will tell them, ‘I never knew you. Depart from me, you who work iniquity.’
John 15:1 “I am the true vine, and my Father is the farmer. 2 Every branch in me that doesn’t bear fruit, he takes away. Every branch that bears fruit, he prunes, that it may bear more fruit. 3 You are already pruned clean because of the word which I have spoken to you. 4 Remain in me, and I in you. As the branch can’t bear fruit by itself, unless it remains in the vine, so neither can you, unless you remain in me. 5 I am the vine. You are the branches. He who remains in me, and I in him, the same bears much fruit, for apart from me you can do nothing. 6 If a man doesn’t remain in me, he is thrown out as a branch, and is withered; and they gather them, throw them into the fire, and they are burned. 7 If you remain in me, and my words remain in you, you will ask whatever you desire, and it will be done for you.
Jesus does not explain what “fruit” is. But He calls it “good fruit,” and says that we must remain in Him in order to produce it. The fruit is probably two related things: influencing people to be converted, and the Fruits of the Spirit, described in Galatians 5, which also describes bad fruit:
Galatians 5:19 Now the deeds of the flesh are obvious, which are: adultery, sexual immorality, uncleanness, lustfulness, 20 idolatry, sorcery, hatred, strife, jealousies, outbursts of anger, rivalries, divisions, heresies, 21 envy, murders, drunkenness, orgies, and things like these; of which I forewarn you, even as I also forewarned you, that those who practice such things will not inherit the Kingdom of God.
22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faith, 23 gentleness, and self-control. Against such things there is no law. 24 Those who belong to Christ have crucified the flesh with its passions and lusts. 25 If we live by the Spirit, let’s also walk by the Spirit. 26 Let’s not become conceited, provoking one another, and envying one another.
A person who is saved is not a habitual sinner.
(Note: To some people, sin is anything short of perfection – to them, honest mistakes, and memory lapses, are sin. However, I am using a more restrictive definition, from the Free Dictionary:
We should remember that there are sins of omission – things that we should do, but don’t – as well as sins of commission. See James 4:17 and Matthew 25:40-25.)
1 John 1:1 My little children, I write these things to you so that you may not sin. If anyone sins, we have a Counselor with the Father, Jesus Christ, the righteous. 2 And he is the atoning sacrifice for our sins, and not for ours only, but also for the whole world.
Romans 6:1 What shall we say then? Shall we continue in sin, that grace may abound? 2 May it never be! We who died to sin, how could we live in it any longer? 3 Or don’t you know that all we who were baptized into Christ Jesus were baptized into his death? 4 We were buried therefore with him through baptism to death, that just as Christ was raised from the dead through the glory of the Father, so we also might walk in newness of life. 5 For if we have become united with him in the likeness of his death, we will also be part of his resurrection; 6 knowing this, that our old man was crucified with him, that the body of sin might be done away with, so that we would no longer be in bondage to sin. 7 For he who has died has been freed from sin. 8 But if we died with Christ, we believe that we will also live with him; 9 knowing that Christ, being raised from the dead, dies no more. Death no more has dominion over him! 10 For the death that he died, he died to sin one time; but the life that he lives, he lives to God. 11 Thus consider yourselves also to be dead to sin, but alive to God in Christ Jesus our Lord.
12 Therefore don’t let sin reign in your mortal body, that you should obey it in its lusts. 13 Also, do not present your members to sin as instruments of unrighteousness, but present yourselves to God, as alive from the dead, and your members as instruments of righteousness to God. 14 For sin will not have dominion over you. For you are not under law, but under grace. 15 What then? Shall we sin, because we are not under law, but under grace? May it never be!
A person who is saved follows Christ’s commandments.
John 14:21 One who has my commandments, and keeps them, that person is one who loves me. One who loves me will be loved by my Father, and I will love him, and will reveal myself to him.”
23 Jesus answered him, “If a man loves me, he will keep my word. My Father will love him, and we will come to him, and make our home with him. 24 He who doesn’t love me doesn’t keep my words.
John 17:15 I pray not that you would take them from the world, but that you would keep them from the evil one. 16 They are not of the world even as I am not of the world. 17 Sanctify them in your truth. Your word is truth. 18 As you sent me into the world, even so I have sent them into the world.
1 John 2:3 This is how we know that we know him: if we keep his commandments. 4 One who says, “I know him,” and doesn’t keep his commandments, is a liar, and the truth isn’t in him. 5 But whoever keeps his word, God’s love has most certainly been perfected in him. This is how we know that we are in him: 6 he who says he remains in him ought himself also to walk just like he walked.
Matthew 7:24 “Everyone therefore who hears these words of mine, and does them, I will liken him to a wise man, who built his house on a rock. 25 The rain came down, the floods came, and the winds blew, and beat on that house; and it didn’t fall, for it was founded on the rock. 26 Everyone who hears these words of mine, and doesn’t do them will be like a foolish man, who built his house on the sand. 27 The rain came down, the floods came, and the winds blew, and beat on that house; and it fell—and great was its fall.”
For more on what Christ's commandments are, see here.
A person who is saved continues in a relationship with Christ, and seeks the fellowship of other Christians.
John 15:1-7 (quoted above) uses the phrase “remain in me” or equivalent, seven times.
John 17:20 Not for these only do I pray, but for those also who believe in me through their word, 21 that they may all be one; even as you, Father, are in me, and I in you, that they also may be one in us; that the world may believe that you sent me. 22 The glory which you have given me, I have given to them; that they may be one, even as we are one; 23 I in them, and you in me, that they may be perfected into one; that the world may know that you sent me, and loved them, even as you loved me.
Hebrews 10:24 Let us consider how to provoke one another to love and good works, 25 not forsaking our own assembling together, as the custom of some is, but exhorting one another; and so much the more, as you see the Day approaching.
There are about 20 occurrences of groups of Christians being together in Acts. Sometimes they met to worship, sometimes as a prayer meeting, sometimes to consider policy or doctrine. It was Paul’s practice to establish churches wherever he went as a missionary. Christ speaks to seven churches, not individuals, in Revelation.
To summarize the evidences given above for being a Christian, a Christian becomes more and more like Christ. The Holy Spirit works in the life of a believer to bring these things about.
August 19, 2012: This document, slightly modified, was re-posted, with a graphic at the beginning, a few days later, here.