Commenting on Philippians 1:5, William Hendriksen writes of the following characteristics of the fellowship of all believers in Christ:-

1. It is a fellowship of grace. It is not natural to us; nor is is manufactured by us.  It is effects by Jesus Christ, 1 Cor. 1:9, and is the gift of the Spirit, 2 Cor. 13:13; Phil. 2:1, who has been sent from the Father.

2. It is a fellowship of faith. As Christ draws us to himself, so we approach him through faith.  By this faith we participate in Christ’s sufferings, body, and blood (Phil. 3:10; 1 Cor. 10:16; 2 Cor. 1:7; and cf. Philem. 6), and also his resurrection and glory (Phil. 3:10; Col. 3:1).

3. It is a fellowship in prayer and thanksgiving. Faith expresses itself in individual and united prayer and thanksgiving, Phil. 1:3, 5, 9–11).

4. It is a fellowship of believers with one another. The same Christ who draws us to himself in the same act draws us into a close relationship with one another, Phil. 1:7, 8; 2:2; 4:2; cf. John 13:34).

5. It is a fellowship in helping each other.  We express our fellowship of live by remembering the poor and needy among us, whoever they are, Rom. 15:26; 2 Cor. 8:4. Moreover, we support those engaged in mission in their various nees, Phil. 4:15.

6. It is a fellowship in promoting the work of the gospel, Gal 2:9; Phil. 1:5; cf. 1 Cor. 9:23.

7. It is a fellowship in separation. This may sound paradoxical, but attachment to Christ also means detachment from the world, 2 Cor. 6:14; cf. James 4:4; 1 John 2:15.

8. It is a fellowship in warfare. We struggle side by side against a common enemy, Phil. 1:27–30; 2:25.

(Based on New Testament Commentary on Philippians)