For ye may all prophesy one by one, that all may learn, and all may be comforted.
For ye may - rather, 'For ye can (if you will) all prophesy one by one,' giving way to one another. The "for", justifies (1 Corinthians 14:30), "let the first hold his peace.
That all may learn, and all may be comforted - that if one prophet do not affect the hearers, another may: so that none may go away, unedited.