Again, I write a new commandment to you, which is true in him and in you; because the darkness is passing away, and the true light already shines.
Which then is true, or which is truth. He proves by this reason what he had said; for this one command respecting love, as to our conduct in life, constitutes the whole truth of Christ. Besides, what other greater revelation can be expected? for Christ, doubtless, is the end and the completion of all things. Hence the word truth means this, that they stood, as it were at the goal, for it is to be taken for a completion or a perfect state. He joins Christ to them, as the head to the members, as though he had said, that the body of the Church has no other perfection, or, that they would then be really united to Christ, if holy love existed continually among them. 