But, speaking the truth. Having already said that we ought not to be children, destitute of reason and judgment, he now enjoins us to grow up in the truth. [1] Though we have not arrived at man's estate, we ought at least, as we have already said, to be advanced children. The truth of God ought to have such a firm hold of us, that all the contrivances and attacks of Satan shall not draw us from our course; and yet, as we have not hitherto attained full and complete strength, we must make progress until death. He points out the design of this progress, that Christ may be the head, "that in all things he may have the pre-eminence," (Colossians 1:18,) and that in him alone we may grow in vigor or in stature. Again, we see that no man is excepted; all are enjoined to be subject, and to take their own places in the body. What aspect then does Popery present, but that of a crooked, deformed person? Is not the whole symmetry of the church destroyed, when one man, acting in opposition to the head, refuses to be reckoned one of the members? The Papists deny this, and allege that the Pope is nothing more than a ministerial head. But such cavils do them no service. The tyranny of their idol must be acknowledged to be altogether inconsistent with that order which Paul here recommends. In a word, a healthful condition of the church requires that Christ alone "must increase," and all others "must decrease." (John 3:30.) Whatever increase we obtain must be regulated in such a manner, that we shall remain in our own place, and contribute to exalt the head. When he bids us give heed to the truth in love, he uses the preposition in, (en,) like the corresponding Hebrew preposition v, (beth,) as signifying with, -- speaking the truth With love [2] If each individual, instead of attending exclusively to his own concerns, shall desire mutual intercourse, there will be agreeable and general progress. Such, the Apostle assures us, must be the nature of this harmony, that men shall not be suffered to forget the claims of truth, or, disregarding them, to frame an agreement according to their own views. This proves the wickedness of the Papists, who lay aside the word of God, and labor to force our compliance with their decisions.

Footnotes

1 - " 'Aletheuontes does not seem properly to denote so much speaking the truth,' as embracing and adhering to it;' and, to render the Christian perfect, he must add to this regard to truth, love, or universal affection and benevolence. It was a noble saying of Pythagoras, agreeable to this sentiment of our apostle, These are the two loveliest gifts of the gods to men, to te aletheuein kai to euergetein, to embrace the truth, and be beneficent.' AElian. 1. 12, c. 58.)" -- Chandler.

2 - " 'Algtheuontes en agape, means much more than speaking the truth in love;' it signifies thinking, feeling, acting under the influence of the truth, which worketh by love.'" -- Brown.

But speaking the truth in love - Margin, "being sincere." The translation in the text is correct - literally, "truthing in love" - ἀληθεύοντες alētheuontes. Two things are here to be noted:
(1) The truth is "to be spoken" - the simple, unvarnished truth. This is the way to avoid error, and this is the way to preserve others from error. In opposition to all trick, and art, and cunning, and fraud, and deception, Christians are to speak the simple truth, and nothing but the truth. Every statement which they make should be unvarnished truth; every promise which they make should be true; every representation which they make of the sentiments of others should he simple truth. "Truth is the representation of things as they are;" and there is no virtue that is more valuable in a Christian than the love of simple truth.
(2) the second thing is, that the truth should be spoken "in love." There are other ways of speaking truth. It is sometimes spoken in a harsh, crabby, sour manner, which does nothing but disgust and offend When we state truth to others, it should he with love to their souls, and with a sincere desire to do them good. When we admonish a brother of his faults, it should not be in a harsh and unfeeling manner, but in love. Where a minister pronounces the awful truth of God about depravity, death, the judgment, and future woe, it should be in love. It should not be done in a harsh and repulsive manner; it should not he done as if he rejoiced that people were in danger of hell, or as if he would like to pass the final sentence; it should not be with indifference, or in a tone of superiority. And in like manner, if we go to convince one who is in error, we should approach him in love. We should not dogmatize, or denounce, or deal out anathemas. Such things only repel. "He has done about half his work in convincing another of error who has first convinced him that he loves him;" and if he does not do that, he may argue to the hour of his death and make no progress in convincing him.
May grow up into him - Into Christ; that is, to the stature of a complete man in him.
Which is the head - Ephesians 1:22 note; 1-Corinthians 11:3 note.

But, speaking the truth in love - The truth recommended by the apostle is the whole system of Gospel doctrine; this they are to teach and preach, and this is opposed to the deceit mentioned above. This truth, as it is the doctrine of God's eternal love to mankind, must be preached in love. Scolding and abuse from the pulpit or press, in matters of religion, are truly monstrous. He who has the truth of God has no need of any means to defend or propagate it, but those which love to God and man provides.
Grow up into him - This is a continuance of the metaphor taken from the members of a human body receiving nourishment equally and growing up, each in its due proportion to other parts, and to the body in general. The truth of God should be so preached to all the members of the Church of God, that they may all receive an increase of grace and life; so that each, in whatever state he may be, may get forward in the way of truth and holiness. In the Church of Christ there are persons in various states: the careless, the penitent, the lukewarm, the tempted, the diffident, the little child, the young man, and the father. He who has got a talent for the edification of only one of those classes should not stay long in a place, else the whole body cannot grow up in all things under his ministry.

(11) But speaking the truth in love, may grow up into him in all things, which is the head, [even] Christ:
(11) By earnest affection of the truth and love, we grow up into Christ: for he (being effectual by the ministry of his word, which as the vital Spirit makes alive the whole body in such a way that it nourishes all the limbs of it according to the measure and proportion of each one) quickens and cherishes his Church, which consists of various functions, as of various members, and preserves the need of every one. And from this it follows that neither this body can live without Christ, neither can any man grow up spiritually, who separates himself from the other members.

But speaking the truth in love,.... Either Christ himself, who is the truth, and is to be preached, and always spoken of with strong affection and love; or the Gospel, the word of truth, so called in opposition to that which is false and fictitious; and also to the law, which is shadowish; and on account of its author, the God of truth, and its subject matter, Christ, and the several doctrines of grace; and because the spirit of truth has dictated it, and does direct to it, and owns and blesses it: this, with respect to the ministers of the Gospel, should be spoken openly, honestly, and sincerely, and in love to the souls of men, and in a way consistent with love, in opposition to the secret, ensnaring, and pernicious ways of false teachers; and with respect to private Christians, as they are to receive it in love, so to speak of it to one another from a principle of love, and an affectionate concern for each other's welfare, to the end that they
may grow up into him in all things which is the head, even "Christ": the work of grace upon the soul is a gradual work, and an increase of this in the exercise of faith, hope, love, and spiritual knowledge, is a growth; and this is a growth in all things, in all grace, as in those mentioned, so in others, as humility, patience, self-denial, resignation of the will to the will of God, and especially the knowledge of Christ; for it is a growing into him, from whom souls receive all their grace and increase of it; for he is the head of influence to supply them, as well as the head of eminence to protect them; see Ephesians 1:22 and now the preaching of the Gospel, or the sincere speaking of the truth, is the instrumental means of such growth.

speaking the truth--Translate, "holding the truth"; "following the truth"; opposed to "error" or "deceit" (Ephesians 4:14).
in love--"Truth" is never to be sacrificed to so-called "charity"; yet it is to be maintained in charity. Truth in word and act, love in manner and spirit, are the Christian's rule (compare Ephesians 4:21, Ephesians 4:24).
grow up--from the state of "children" to that of "full-grown men." There is growth only in the spiritually alive, not in the dead.
into him--so as to be more and more incorporated with Him, and become one with Him.
the head-- (Ephesians 1:22).

Into him - Into his image and Spirit, and into a full union with him.