Exactly what is a Christian? How does the Bible define a Christian in the most accurate sense?
The Scriptures clearly identify who belongs to Christ—that is, who we might term a true Christian. Notice the apostle Paul's teaching in Romans 8:9 Romans 8:9But you are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
American King James Version×: "Now if anyone does not have the Spirit of Christ, he is not His" (emphasis added throughout). The Holy Spirit, then, is an essential aspect of the biblical definition of a Christian. Further, only those who are led by God's Spirit have access to eternal life.
Paul continues in verse 11, "But if the Spirit of Him who raised Jesus from the dead dwells in you, He who raised Christ from the dead will also give life to your mortal bodies through His Spirit [which] dwells in you."
It becomes abundantly clear that the Holy Spirit plays a major role in the lives of Christians. In verse 14 Paul defines the Christian very clearly: "For as many as are led by the Spirit of God, these are sons of God." The Holy Spirit identifies us with Christ (verse 9), it makes immortality possible to human, mortal beings (verse 11), it makes possible an obedient, overcoming Christian life (verse 13), and it truly leads (guides, empowers and motivates) the sons of God. In short, God's Spirit—also called the Spirit of Christ—is what makes one a Christian, a Spirit-led follower of Jesus Christ.
If the Holy Spirit is what defines a Christian and makes one a child of God, it is most vital that we learn and understand more about that Spirit and its role.
A force for change
The Holy Spirit is described in the Bible as a power at work in the lives of people, dealing with them and revealing more fully God and His will for mankind.
In Galatians 5:22-23 Galatians 5:22-23  But the fruit of the Spirit is love, joy, peace, long-suffering, gentleness, goodness, faith,
 Meekness, temperance: against such there is no law.
American King James Version×we have a description of the fruit the Holy Spirit produces in a person's life—"love, joy, peace, longsuffering, kindness, goodness, faithfulness, gentleness, self-control." The Holy Spirit is associated with God's divine character. It serves in the capacity of a "Comforter" or Helper" to a Christian (John 16:7 John 16:7Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come to you; but if I depart, I will send him to you.
American King James Version×)—assisting in helping us to develop the righteousness of God.
In Romans 5:5 Romans 5:5And hope makes not ashamed; because the love of God is shed abroad in our hearts by the Holy Ghost which is given to us.
American King James Version×we read, "Now hope does not disappoint, because the love of God has been poured out in our hearts by the Holy Spirit [which] was given to us." Here the Spirit is described as God's gift to us, God's love flowing to us and through us toward others. The overwhelming and majestic truth is that God promises this to us, and we can have access to this matchless and priceless gift.
How do we receive the Holy Spirit? What will the Spirit do in our lives?
How to receive God's Spirit
In Luke 24:45 Luke 24:45Then opened he their understanding, that they might understand the scriptures,
American King James Version×Jesus "opened their understanding, that they might comprehend the Scriptures." He had just explained that the Law, the Prophets and the Writings prophesied of Him, and the disciples had just witnessed the fulfillment of many of those prophecies. He explained His death and resurrection and told them that they were witnesses to these things and that repentance and remission of sins would be preached to all nations, beginning at Jerusalem (verse 46-47).
But to be able to play their part they needed something they didn't have. After all, just a few days earlier they all had forsaken Him and fled in fear for their lives. Jesus knew this and reassured them: "Behold, I send the promise of My Father upon you; but tarry in the city of Jerusalem until you are endued with power from on high" (verse 49). The same writer, Luke, again picks up that admonition in Acts 1:4-5 Acts 1:4-5  And, being assembled together with them, commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which, said he, you have heard of me.
 For John truly baptized with water; but you shall be baptized with the Holy Ghost not many days hence.
American King James Version×, where Christ told the disciples to stay in Jerusalem until they received the Holy Spirit.
Acts 2 records the miraculous giving of the Holy Spirit on the Day of Pentecost after Christ's death and resurrection. The Holy Spirit was given with mighty power to inspire and motivate the 120 disciples assembled in Jerusalem—and later that day thousands more. As Peter's first inspired sermon drew to a close, the people hearing him were "cut to the heart, and said to Peter and the rest of the apostles, 'Men and brethren, what shall we do?' " (verses 37). They wanted to be forgiven of their sins and to receive the Holy Spirit, which they witnessed at work in the lives of Christ's followers!
The same condition applies today. We all need forgiveness. We all need God's Spirit. Peter's answer to the people's question was: "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit. For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call" (verses 38-39).
Could any instructions be clearer? To receive His Spirit God calls on us to repent—to change our frame of mind, our entire outlook on life, surrendering our wills to Him. Then He tells us to be baptized. In Acts 8:12-22 Acts 8:12-22  But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
 Then Simon himself believed also: and when he was baptized, he continued with Philip, and wondered, beholding the miracles and signs which were done.
 Now when the apostles which were at Jerusalem heard that Samaria had received the word of God, they sent to them Peter and John:
 Who, when they were come down, prayed for them, that they might receive the Holy Ghost:
 (For as yet he was fallen on none of them: only they were baptized in the name of the Lord Jesus.)
 Then laid they their hands on them, and they received the Holy Ghost.
 And when Simon saw that through laying on of the apostles' hands the Holy Ghost was given, he offered them money,
 Saying, Give me also this power, that on whomsoever I lay hands, he may receive the Holy Ghost.
 But Peter said to him, Your money perish with you, because you have thought that the gift of God may be purchased with money.
 You have neither part nor lot in this matter: for your heart is not right in the sight of God.
 Repent therefore of this your wickedness, and pray God, if perhaps the thought of your heart may be forgiven you.
American King James Version×we find that, once one repents in faith and is baptized, he receives the Holy Spirit through the laying on of hands.
Notice what Paul instructs Timothy, an evangelist and Paul's "son in the faith," in 2 Timothy 1:6-7 2 Timothy 1:6-7  Why I put you in remembrance that you stir up the gift of God, which is in you by the putting on of my hands.
 For God has not given us the spirit of fear; but of power, and of love, and of a sound mind.
American King James Version×: "Therefore I remind you to stir up the gift of God which is in you through the laying on of my hands. For God has not given us a spirit of fear, but of power and of love and of a sound mind." To have that sound mind—the mind of Christ (Philippians 2:5 Philippians 2:5Let this mind be in you, which was also in Christ Jesus:
American King James Version×; 1 Corinthians 2:16 1 Corinthians 2:16For who has known the mind of the Lord, that he may instruct him? But we have the mind of Christ.
American King James Version×)—we must have God's Spirit.
Christ's instruction about the Holy Spirit
We have briefly covered how God's Spirit comes into our life. But what will the Spirit do in our life? What is its role?
The apostle John was inspired to record much of Jesus Christ's description of the role of the Holy Spirit. Knowing that He would soon die and thereby leave them, Jesus instructed the disciples about the power soon to come on them. "If you love me, keep My commandments," He told them, "and I will pray the Father, and He will give you another Helper [the Holy Spirit is to help, strengthen, nurture us], that He may abide with you forever" (John 14:15-16 John 14:15-16  If you love me, keep my commandments.
 And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever;
American King James Version×).
Verses 17-18 explain that the Holy Spirit is the Spirit of Truth that would dwell in them and be with them. In verse 26 Christ said of this Spirit, "But the Helper, the Holy Spirit, [which] the Father will send in My name, [it] will teach you all things, and bring to your remembrance all things that I said to you." The Spirit, then, would make the writing of the Gospels possible and guide Christ's followers in spiritual understanding.
John 16 records more of Christ's instruction about the role of the Holy Spirit. "It is to your advantage that I go away; for if I do not go away, the Helper will not come to you; but if I depart, I will send [it] to you" (verse 7).
How the Holy Spirit functions
Christ showed three distinct workings of the Holy Spirit. "And when [it] has come, [it] will convict the world of sin . . ." (verse 8). When some were "cut to the heart" on the Day of Pentecost (Acts 2:37 Acts 2:37Now when they heard this, they were pricked in their heart, and said to Peter and to the rest of the apostles, Men and brothers, what shall we do?
American King James Version×), how had they come to be in that condition, recognizing their true spiritual state and knowing they needed help? It was through the convicting power of God's Spirit.
This same Spirit prompted the Ethiopian eunuch to beg of Phillip, "What hinders me from being baptized?" (Acts 8:36 Acts 8:36And as they went on their way, they came to a certain water: and the eunuch said, See, here is water; what does hinder me to be baptized?
American King James Version×). It brought Paul to his knees, crying out "Lord, what do You want me to do?" (Acts 9:6 Acts 9:6And he trembling and astonished said, Lord, what will you have me to do? And the Lord said to him, Arise, and go into the city, and it shall be told you what you must do.
American King James Version×). It caused the Philippian jailer, who had earlier beaten and chained Paul and Silas, to fall down trembling before them, pleading, "Sirs, what must I do to be saved?" (Acts 16:30 Acts 16:30And brought them out, and said, Sirs, what must I do to be saved?
American King James Version×).
Paul tells us that "the goodness of God leads you to repentance" (Romans 2:4 Romans 2:4Or despise you the riches of his goodness and forbearance and long-suffering; not knowing that the goodness of God leads you to repentance?
American King James Version×). Through His Spirit, God helps us to see our true spiritual condition and recognize our need for repentance—to change and begin living God's way. Then we must act on that conviction: repent, be baptized and receive God's Spirit through the laying on of hands of God's ministry, as discussed earlier.
A second function of God's Spirit, as recorded in John 16:8 John 16:8And when he is come, he will reprove the world of sin, and of righteousness, and of judgment:
American King James Version×, is to "convict the world of sin, and of righteousness." After we are forgiven of our sins, can we just go back into sin? Paul clearly explains that we can't. In Romans 6 Paul describes the transformed life of a Christian being truly led by God's Spirit. Having once served sin, we now serve a new master: God's righteousness.
"But God be thanked that though you were slaves of sin [until the Holy Spirit convicted us to repent and come out of sin], yet you obeyed from the heart that form of doctrine to which you were delivered. And having been set free from sin [forgiven and paid for by the blood of Jesus Christ], you became slaves of righteousness [right doing and adherence to God's laws]" (Romans 6:17-18 Romans 6:17-18  But God be thanked, that you were the servants of sin, but you have obeyed from the heart that form of doctrine which was delivered you.
 Being then made free from sin, you became the servants of righteousness.
American King James Version×).
Leaving a life of sin and beginning a new life of humble obedience to God's laws marks the life of those led by God's Spirit (Psalms 119:172 Psalms 119:172My tongue shall speak of your word: for all your commandments are righteousness.
American King James Version×; 1 John 3:7-10 1 John 3:7-10  Little children, let no man deceive you: he that does righteousness is righteous, even as he is righteous.  He that commits sin is of the devil; for the devil sins from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.  Whoever is born of God does not commit sin; for his seed remains in him: and he cannot sin, because he is born of God.  In this the children of God are manifest, and the children of the devil: whoever does not righteousness is not of God, neither he that loves not his brother.
American King James Version×; 1 John 5:17 1 John 5:17All unrighteousness is sin: and there is a sin not to death.
American King James Version×).
The third function of God's Spirit mentioned in John 16 is that it would "convict the world . . . of judgment." The Holy Spirit keeps us aware that "we shall all stand before the judgment seat of Christ" and that "every knee shall bow to Me, and every tongue shall confess to God" (Romans 14:10-11 Romans 14:10-11  But why do you judge your brother? or why do you set at nothing your brother? for we shall all stand before the judgment seat of Christ.
 For it is written, As I live, said the Lord, every knee shall bow to me, and every tongue shall confess to God.
American King James Version×). It regularly reminds us that "each of us shall give account of himself to God" (verse 12).
How great is our loving God and Father who has made all things possible through His Son Jesus Christ! (Matthew 19:26 Matthew 19:26But Jesus beheld them, and said to them, With men this is impossible; but with God all things are possible.
American King James Version×). His work within us is accomplished through the greatest gift that could ever be made available for human beings: the power, love and mind of Christ through the Spirit of God at work in our lives. GN