3:16 lay down our lives. The meaning here actually is “be laying down.” That is, for our brethren’s sake, we ought to serve as a daily “living sacrifice” (Romans 12:1).
3:17 seeth. As often seen in this epistle, the verb is in the continuing present—that is, “goes on seeing.” This does not refer to a chance encounter with someone in need, as it would be impossible to help all such, but a continual refusal to help a truly needy fellow Christian with whom we are in frequent contact and who really needs the help we could provide.
3:18 not love in word. True love is not something to write or talk about; it is something we do, “in deed and in truth.” Our love for God is demonstrated, not by preaching or singing about it, but by living it. Note I John 2:5; 2:15; 5:3. In particular, it will be manifested in our relations with other Christians (I John 3:16,17; 4:11,20).