Fellowship with Father, Son and Holy Spirit
In the New Testament the true nature of fellowship has a distinctly spiritual meaning.  Christian fellowship exists only through the New Covenant.  Those who believe in Jesus are joined by the Holy Spirit, through the Son, to God the Father.  Paul emphasises the call into fellowship with Jesus in 1 Corinthians 1:9 "God who has called you into fellowship with His Son, Jesus Christ our Lord, is faithful".  Fellowship is based upon the saving Grace of God.  We can have fellowship (or intimacy) with God only because He has redeemed us as children of God, through faith in Jesus (see Ephesians 2:4-7).  Holy Communion is a practical way of sharing in the realisation of the effects of "the body and the blood" - namely, eternal life with God the Father, through His Son.  This communion and close relationship is divine fellowship.

Fellowship with Jesus also involves sharing in suffering for His sake.  "I want to know Christ and the power of His resurrection and the fellowship of sharing in his sufferings, becoming like Him in death." (Philippians 3:10).  This is dying to our own agendas, our selfish desires, wrong motives to be born again in Christ.  "Therefore if anyone is in Christ, he is a new creation; the old has gone, the new has come" (2 Corinthians 5:17).  Believers in Christ are united with Him in the Holy Spirit; they are a new creation.

Fellowship with Others
Those who are "in Christ" are called not only to fellowship/communion with God but also with one another.  "We proclaim to you what we have seen and heard, so that you also may have fellowship with us.  And our fellowship is with the Father and with his Son, Jesus Christ" (1 John 1:3) and again, "If we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin."  (1 John 1:7) .  Those who have fellowship with Christ ought to have fellowship with other believers.  Hebrews 10:24-25 reminds us "Let us consider how we may spur one another on towards love and good deeds.  Let us not give up meeting together, as some are in the habit of doing, but let us encourage one another - and all the more as you see the Day approaching". And the character of this fellowship ought to illustrate the very nature of God Himself.  In John  13:35 we hear Jesus' words: "By this all men will know that you are my disciples, if you love one another".  And in Ephesians 5:1 "Be imitators of God...".  We are required to seek out the mind of Christ and, having done so, to follow His holy example. "But just as He who called you is Holy, so be holy in all you do; for it is written: Be holy, because I am holy" (1 Peter 1:15-16).   In Acts 2:42-47, we read about the fellowship of the believers and how they interacted with one another, and in Romans 14:19 we see how Paul called believers to  "make every effort to do what leads to peace and to mutual edification" in order to promote love and Christian fellowship/brotherhood.

In the bible we learn not only about fellowship with believers, but we are also warned against fellowship with unbelievers.  It is clear that believers are not to have fellowship with unbelievers.  However, this does NOT mean that believers should have nothing to do with unbelievers.  The bible plainly teaches that believers are obligated to share the gospel with unbelievers (See Matthew 28:16-20,  Mark 16:15-16, 1 Corinthians 9:16-17). However, believers must not share in unbelievers sinful lifestyles: "Do not be yoked together with unbelievers.  For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness?" (2 Corinthians 6:14-15).  Believers are to come out and be separate.

Fellowship Responsibilities
Christian fellowship also carries with it some practical responsibilities.  Paul teaches us of sharing, in practical terms, within the wider church.  He also reminds us, in Romans 11, of our debt to Israel.  Salvation is of the Jews - without the Jewish nation we would not have our Bible or indeed our Saviour!  The Bible makes it clear that we are to acknowledge our spiritual debt to the Jewish people and try to repay it through mercy, kindness and love - characteristics of true Christian fellowship. "For as you [Gentiles] were once disobedient to God, yet have now obtained mercy through their [the Jews] disobedience, even so these [Jews] also have now been disobedient that through mercy shown you [the Gentiles], they [the Jews] may also obtain mercy."  (Romans 11:30-31).

A feeling of responsiblity for the spiritual well-being of other believers also plays an important part in Christian fellowship.  James 5:16 tells us to "Confess your sins to each other and pray for each other..." and later in verse 19-20 "... if one of you should wander from the truth and someone should bring him back, remember this: whoever turns a sinner from the error of his way will save him from death ..."  Responsibility one for each other through trust and love.  Lovett H Weems notes that Rev John Wesley, writing about the failure of true fellowship in the church, said: "Look east or west, north or south; name what parish you please: is this Christian fellowship there?  Rather, are not the bulk of parishioners a mere rope of sand?  What Christian connection is there between them? What intercourse in spiritual things?  What watching over each other's souls?  What bearing of one another's burdens?"  John Wesley set up the class meeting (or house group) to, in his words, "introduce fellowship where it was utterly destroyed".  He firmly believed in the necessity of mutual encouragement, prayer and service.

Conclusion
So, "fellowship" is a word with deep meaning and purpose.  We can define it as many things:  communion, intimacy, sharing, connection, partnership, common experience, companionship, co-working, mutual encouragement and participation.  As we've seen, fellowship means much more than soup lunches, daffodil teas and nice church socials!  Such "get-togethers" are fun but it should be recognised that they are simply by-products arising from something that should exist much deeper. They can never, in themselves, produce that sincere, burden-bearing, soul-watching kind of fellowship that believers are to enjoy.  We must not be tempted to "put the cart before the horse"!  True Christian fellowship is to partake with like-minded believers in the divine nature of God, through Christ Jesus, so as to bear one another up in love, for His Glory.