This is sometimes translated “communion” in the KJV (i.e. 1 Cor. 10:16). It means to be “partakers together” in that which the parties involved have in common. Believers on the Lord Jesus Christ have been brought into “fellowship” with the Father and the Son (1 John 1:3), with the Holy Spirit (2 Cor. 13:14), and with one another (1 John 1:7). Thus, abiding together in this fellowship, God and His people have their hearts knit together in intelligent thought, aim, purpose, desire, and affection regarding all things past, present, and future. If our thoughts and ideas are not in accord with the mind of God, then we are out of communion with Him, as far as those topics are concerned.
Fellowship of this kind does not appear in Scripture until after atonement was made, whereupon God has come out to man in grace to form a relationship with believers in the light of the full revelation of truth. Old Testament saints such as Abraham had communion with God, but not in the way in which Christians know communion with God by the indwelling Spirit. H. M. Hooke said, “The first time it [fellowship] occurs in the New Testament is in Acts 2:42. Why don’t you get it before? Because until you have eternal life revealed, manifested, and until it was communicated, there could be no such thing as fellowship. How could God take people into fellowship with Himself until He put their sins away? It is not until Christ died, rose again, and went to heaven, and the Holy Ghost came down, that you get that word” (The Christian Friend, vol. 12 [1885], p. 234).
In Scripture, Christian fellowship (1 Cor. 1:9; Acts 2:42-47) is all about togetherness. It involves being gathered “together” unto the name of the Lord Jesus Christ (Matt. 18:20), coming “together” for the breaking of bread (Acts 20:7), assembling “together” for prayer (Acts 4:31; 12:12; Rom. 15:30), assembling “together” for ministry from the Word (Acts 11:26; 1 Cor. 14:23), assembling “together” for administrative actions (Acts 15:30; 1 Cor. 5:4), being “together” for mutual comfort and encouragement (Rom. 1:12), walking “together” with one mind and with the same objectives (1 Cor. 1:10), and being labourers “together” in the service of the Lord (1 Cor. 3:9; 2 Cor. 6:1).
All this is based on the fact that we have been quickened “together,” raised up “together,” and seated “together” in Christ (Eph. 2:5-6), and also because we have been fitly framed “together” (Eph. 2:21) and builded “together” for a habitation for God on earth (Eph. 2:22). Soon we will be caught up “together,” and thus gathered “together” to Him (2 Thess. 2:1), being glorified “together” (Rom. 8:17), and ultimately we will live “together” with Him (1 Thess. 5:10).