To that gospel, to that Lord, the walk, the active life, is to be conformed, and the manner thereof is more fully explained in the following clauses.
"Rooted and built up in Him." Here again we have the profound "in Him," which appears so frequently in this and in the companion Epistle to the Ephesians, and which must be allowed its proper force, as expressing a most real indwelling of the believer in Christ, if the depth of the meaning is to be sounded.
Paul drives his fiery chariot through rhetorical proprieties, and never shrinks from "mixed metaphors" if they more vigorously express his thought. Here we have three incongruous ones close on each other's heels. The Christian is to _walk_, to be _rooted_ like a tree, to be _built up_ like a house. What does the incongruity matter to Paul as the stream of thought and feeling hurries him along?
The tenses of the verbs, too, are studiously and significantly varied. Fully rendered they would be "having been rooted and being builded up." The one is a past act done once for all, the effects of which are permanent; the other is a continuous resulting process which is going on now. The Christian has been rooted in Jesus Christ at the beginning of his Christian course. His faith has brought him into living contact with the Saviour, who has become as the fruitful soil into which the believer sends his roots, and both feeds and anchors there. The familiar image of the first Psalm may have been in the writer's mind, and naturally recurs to ours. If we draw nourishment and stability from Christ, round whom the roots of our being twine and cling, we shall flourish and grow and bear fruit. No man can do without some person beyond himself on whom to repose, nor can any of us find in ourselves or on earth the sufficient soil for our growth. We are like seedlings dropped on some great rock, which send their rootlets down the hard stone and are stunted till they reach the rich leaf-mould at its base. We blindly feel through all the barrenness of the world for something into which our roots may plunge that we may be nourished and firm. In Christ we may be "like a tree planted by the river of water;" out of Him we are "as the chaff," rootless, lifeless, profitless, and swept at last by the wind from the threshing floor. The choice is before every man--either to be rooted in Christ by faith, or to be rootless.
"Being built up in Him." The gradual continuous building up of the structure of a Christian character is doubly expressed in this word by the present tense which points to a process, and by the prefixed preposition represented by "up," which points to the successive laying of course of masonry upon course. We are the architects of our own characters. If our lives are based on Jesus Christ as their foundation, and every deed is in vital connection with Him, as at once its motive, its pattern, its power, its aim, and its reward, then we shall build holy and fair lives, which will be temples. Men do not merely grow as a leaf which "grows green and broad, and takes no care." The other metaphor of a building needs to be taken into account, to complete the former. Effort, patient continuous labour must be put forth. More than "forty and six years is this temple in building." A stone at a time is fitted into its place, and so after much toil and many years, as in the case of some mediaeval cathedral unfinished for centuries, the topstone is brought forth at last. This choice, too, is before all men--to build on Christ and so to build for eternity, or on sand and so to be crushed below the ruins of their fallen houses.