One plain principle implied here is that the only true fruit is goodness. We may be busy, as many a man in our great commercial cities is busy, from Monday morning till Saturday night for a long lifetime, and may have had to build bigger barns for our "fruits and our goods," and yet, in the high and solemn meaning of the word here, our life may be utterly empty and fruitless. Much of our work and of its results is no more fruit than the galls on the oak-leaves are. They are a swelling from a puncture made by an insect, a sign of disease, not of life. The only sort of work which can be called fruit, in the highest meaning of the word, is that which corresponds to a man's whole nature and relations; and the only work which does so correspond is a life of loving service of God, which cultivates all things lovely and of good report. Goodness, therefore, alone deserves to be called fruit--as for all the rest of our busy lives, they and their toils are like the rootless, lifeless chaff that is whirled out of the threshing-floor by every gust. A life which has not in it holiness and loving obedience, however richly productive it may be in lower respects, is in inmost reality blighted and barren, and is "nigh unto burning." Goodness is fruit; all else is nothing but leaves.
Again: the Christian life is to be "fruitful in _every_ good work." This tree is to be like that in the apocalyptic vision, which "bare twelve manner of fruits," yielding every month a different sort. So we should fill the whole circuit of the year with various holiness, and seek to make widely different forms of goodness our own. We have all certain kinds of excellence which are more natural and easier for us than others are. We should seek to cultivate the kind which is hardest for us. The thorn stock of our own character should bear not only grapes, but figs too, and olives as well, being grafted upon the true olive-tree, which is Christ. Let us aim at this all-round and multiform virtue, and not be like a scene for a stage, all gay and bright on one side, and dirty canvas and stretchers hung with cobwebs on the other.
The second element in the analysis of the true Christian life is--"increasing in the knowledge of God." The figure of the tree is probably continued here. If it fruits, its girth will increase, its branches will spread, its top will mount, and next year its shadow on the grass will cover a larger circle. Some would take the "knowledge" here as the instrument or means of growth, and would render "increasing by the knowledge of God," supposing that the knowledge is represented as the rain or the sunshine which minister to the growth of the plant. But perhaps it is better to keep to the idea conveyed by the common rendering, which regards the words "in knowledge" as the specification of that region in which the growth enjoined is to be realized. So here we have the converse of the relation between work and knowledge which we met in the earlier part of the chapter. There, knowledge led to a worthy walk; here, fruitfulness in good works leads to, or at all events is accompanied with, an increased knowledge. And both are true. These two work on each other a reciprocal increase. All true knowledge which is not mere empty notions, naturally tends to influence action, and all true action naturally tends to confirm the knowledge from which it proceeds. Obedience gives insight: "If any man wills to do My will, he shall know of the doctrine." If I am faithful up to the limits of my present knowledge, and have brought it all to bear on character and conduct, I shall find that in the effort to make my every thought a deed, there have fallen from my eyes as it were scales, and I see some things clearly which were faint and doubtful before. Moral truth becomes dim to a bad man. Religious truth grows bright to a good one, and whosoever strives to bring all his creed into practice, and all his practice under the guidance of his creed, will find that the path of obedience is the path of growing light.