And (κα). Mutual fellowship depends on mutual knowledge (Westcott).

Message (αγγελια). Old word (from αγγελος, messenger), in N.T. only here and 1. John 3:11, and note απ' αυτου (from God like απαγγελλω in verse 1. John 1:3) and αναγγελλομεν, to announce, to disclose, here as in John 4:25.

God is light (ο θεος φως εστιν). Precisely so the Λογος is light (John 1:4-9) and what Jesus claimed to be (John 8:12). John repeats it in negative form as he often does (John 1:3).