For your fellowship in the gospel from the first day until now;
Cause for his 'thanking God' (as Philippians 1:3 marks the object on which his thanks rest, and Philippians 1:4 when he gives thanks).
For your fellowship (i:e., real spiritual participation) in (literally, 'in regard to,' or 'into:' Greek, Matthew 28:19)
The gospel from the first day (of your becoming partakers in it) until now (Acts 2:42; Acts 16:13). Believers have the Gospel fellowship of the Son (1 Corinthians 1:9) and of the Father (1 John 1:3), by becoming partakers of "the fellowship of the Holy Spirit" (2 Corinthians 13:14), and exercise it by acts of communion, not only the Lord's supper, but holy liberality to brethren and ministers (Philippians 4:10; Philippians 4:15, "communicated with me, as concerning giving;" 2 Corinthians 9:13; Galatians 6:6; Hebrews 13:16).