The word "Christian" occurs only 3 times in the Bible. Each occurrence, however, gives us some insight into the debate about who can be called Christian. If you're going to start casting people out from Christianity on the basis of the Bible, you had better start with what the Bible has to say about this term.
Here are the three occurrences, in order: Acts 11:26, Acts 26:28, and 1 Peter 4:16. If you're not willing to accept people's proclamation of belief in Christ as the commonsense and gracious standard for being Christian and instead want a more exclusionary definition rigorously based on the Bible, these are the key verses to understand. Now let's see what they have to teach us, in context.
Acts 11:26, in the Context of Acts 11:15-30
15 And as I began to speak, the Holy Ghost fell on them, as on us at the beginning.In verse 26, we learn that the term "Christian" was what others called the disciples, who in the New Testament tended to call themselves "saints" rather than "Christians" per se (e.g., Acts 9:13, Eph. 2:18-20 and many others). The term obviously stuck and spread and we are certainly happy with it, though "saints" still applies in the original biblical sense. But what do we learn about these people in Antioch who were called Christians? The next verse gives us a telling clue: "And in these days came prophets from Jerusalem unto Antioch." OK. If we want to whittle down the definition of "Christian" based on how the Bible uses that term, we can suggest that real biblical Christians will have prophets among them, or rather be willing to receive prophets sent from Church headquarters.
16 Then remembered I the word of the Lord, how that he said, John indeed baptized with water; but ye shall be baptized with the Holy Ghost.
17 Forasmuch then as God gave them the like gift as he did unto us, who believed on the Lord Jesus Christ; what was I, that I could withstand God?
18 When they heard these things, they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life.
19 Now they which were scattered abroad upon the persecution that arose about Stephen travelled as far as Phenice, and Cyprus, and Antioch, preaching the word to none but unto the Jews only.
20 And some of them were men of Cyprus and Cyrene, which, when they were come to Antioch, spake unto the Grecians, preaching the LORD Jesus.
21 And the hand of the Lord was with them: and a great number believed, and turned unto the Lord.
22 Then tidings of these things came unto the ears of the church which was in Jerusalem: and they sent forth Barnabas, that he should go as far as Antioch.
23 Who, when he came, and had seen the grace of God, was glad, and exhorted them all, that with purpose of heart they would cleave unto the Lord.
24 For he was a good man, and full of the Holy Ghost and of faith: and much people was added unto the Lord.
25 Then departed Barnabas to Tarsus, for to seek Saul:
26 And when he had found him, he brought him unto Antioch. And it came to pass, that a whole year they assembled themselves with the church, and taught much people. And the disciples were called Christians first in Antioch.
27 And in these days came prophets from Jerusalem unto Antioch.
28 And there stood up one of them named Agabus, and signified by the Spirit that there should be great dearth throughout all the world: which came to pass in the days of Claudius Caesar.
29 Then the disciples, every man according to his ability, determined to send relief unto the brethren which dwelt in Judaea:
30 Which also they did, and sent it to the elders by the hands of Barnabas and Saul.
The context of Acts 11 tells us more. It shows a Church suffering persecution, with active apostles and disciples reaching out to diverse geographical regions and doing missionary work. They preached repentance (note "repentance unto life" in verse 18). They had baptism by water and the gift of the Holy Ghost. They had a central organization that sent Church leaders to preach and conduct the work of the Church in remote regions. They exhorted believers to "cleave unto the Lord."
Finally, in light of a prophet warning of famine to come, the Church organized temporal relief efforts to help the saints cope with food shortages.
So far I'm feeling rather comfortable with what the Bible has to say about "Christians." Prophets, gift of the Holy Ghost, baptism, missionary work, organized central ministry with broad outreach via apostles and disciples, and organized Church welfare efforts, and perhaps even something compatible with a food storage program to cope with predicted famine in advance (might be reading too much into the text there). OK, my testimony is still intact.
Acts 26:28, in the Context of Acts 26:22-29
This is Paul's famous encounter with King Agrippa. Here's part of it:
22 Having therefore obtained help of God, I continue unto this day, witnessing both to small and great, saying none other things than those which the prophets and Moses did say should come:Agrippa, not Paul, the term "Christian," but that's no problem. What was the persuading that Paul was doing? He was teaching the basics: that Christ suffered for us, that he was killed and resurrected (yes, a real, physical Resurrection), that there were witnesses of the real and tangible resurrected Lord who had seen Him, and that He continued to be a light to the world. He wasn't getting into fine metaphysics or details of theology and complex interpretations of scripture, but the basics.
23 That Christ should suffer, and that he should be the first that should rise from the dead, and should shew light unto the people, and to the Gentiles.
24 And as he thus spake for himself, Festus said with a loud voice, Paul, thou art beside thyself; much learning doth make thee mad.
25 But he said, I am not mad, most noble Festus; but speak forth the words of truth and soberness.
26 For the king knoweth of these things, before whom also I speak freely: for I am persuaded that none of these things are hidden from him; for this thing was not done in a corner.
27 King Agrippa, believest thou the prophets? I know that thou believest.
28 Then Agrippa said unto Paul, Almost thou persuadest me to be a Christian.
29 And Paul said, I would to God, that not only thou, but also all that hear me this day, were both almost, and altogether such as I am, except these bonds.
Paul, in his teachings, emphasizes the word of the prophets. Again, "prophets" and "Christians" are being paired in the Bible. We also ask the world, "Believest thou the prophets?" Paul, though, was referring to the writings of past prophets, though he himself as an ordained apostle called by Jesus Christ through revelation was also a modern prophet.
We also learn that outsiders like Agrippa called the Christian religion an expression of madness. Check.
Believing in the basics of Christ as Savior and resurrected Lord, accepting apostles and prophets, and being called crazy: testimony still intact.
1 Peter 4:16, in the Context of 1 Peter 4
1 Forasmuch then as Christ hath suffered for us in the flesh, arm yourselves likewise with the same mind: for he that hath suffered in the flesh hath ceased from sin;Hmm. Gospel preached to the dead, list of sins to avoid and emphasis on the need to obey the Gospel, future accountability to God, and need to live in the Spirit now. I'm still OK with this. My testimony has survived yet another challenge. How's that anti-testimony doing, fellow Christian?
2 That he no longer should live the rest of his time in the flesh to the lusts of men, but to the will of God.
3 For the time past of our life may suffice us to have wrought the will of the Gentiles, when we walked in lasciviousness, lusts, excess of wine, revellings, banquetings, and abominable idolatries:
4 Wherein they think it strange that ye run not with them to the same excess of riot, speaking evil of you:
5 Who shall give account to him that is ready to judge the quick and the dead.
6 For for this cause was the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the spirit.
7 But the end of all things is at hand: be ye therefore sober, and watch unto prayer.
8 And above all things have fervent charity among yourselves: for charity shall cover the multitude of sins.
9 Use hospitality one to another without grudging.
10 As every man hath received the gift, even so minister the same one to another, as good stewards of the manifold grace of God.
11 If any man speak, let him speak as the oracles of God; if any man minister, let him do it as of the ability which God giveth: that God in all things may be glorified through Jesus Christ, to whom be praise and dominion for ever and ever. Amen.
12 Beloved, think it not strange concerning the fiery trial which is to try you, as though some strange thing happened unto you:
13 But rejoice, inasmuch as ye are partakers of Christ's sufferings; that, when his glory shall be revealed, ye may be glad also with exceeding joy.
14 If ye be reproached for the name of Christ, happy are ye; for the spirit of glory and of God resteth upon you: on their part he is evil spoken of, but on your part he is glorified.
15 But let none of you suffer as a murderer, or as a thief, or as an evildoer, or as a busybody in other men's matters.
16 Yet if any man suffer as a Christian, let him not be ashamed; but let him glorify God on this behalf.
17 For the time is come that judgment must begin at the house of God: and if it first begin at us, what shall the end be of them that obey not the gospel of God?
18 And if the righteous scarcely be saved, where shall the ungodly and the sinner appear?
19 Wherefore let them that suffer according to the will of God commit the keeping of their souls to him in well doing, as unto a faithful Creator.
Fortunately, I don't require that others pass through all these hoops to be called Christian. If you sincerely believe in Jesus Christ as our Savior, welcome to the club! Of course, there are some very cool things we'd like you to consider adding to your faith to strengthen your covenant relationship with the Lord and your understanding of the majesty of His Atonement, but we can talk about that later.