Colossians 2:2

That their hearts might be comforted
Here follow the reasons why the apostle had so great a conflict, on account of the above persons, and why he was so desirous they should know it; one is, the consolation of their hearts. The hearts of God's people often need comfort, by reason of indwelling sin, the temptations of Satan, the hidings of God's face, and afflictive providences; and by reason of false teachers, who greatly trouble them, unsettle their minds, weaken their faith, and fill them with doubts and perplexities, and which was the case with these churches: now the business of Gospel ministers is to comfort such; this is the commission they are sent with; the doctrines of the Gospel are calculated for this very purpose, such as full redemption, free justification, complete pardon of sin, peace and reconciliation; and the bent of their ministry is to comfort distressed minds, upon what account soever; and it must be a comfort to these churches, when they found that they were regarded by so great an apostle; and it might tend to confirm them in the doctrine they had received at first, and deliver them from the scruples the false apostles had injected into their minds, and so administer comfort to them, when they perceived that the apostle approved of the Gospel they had heard and embraced, and rejected the notions of the false teachers:

being knit together in love:
as the members of an human body are, by joints and bands; as love is the bond of union between God and his people, Christ and his members, so between saints and saints; it is the cement that joins and keeps them together, and which edifies and builds them up, and whereby they increase with the increase of God; it makes them to be of one heart and one soul; it renders their communion with one another comfortable and delightful, and strengthens them against the common enemy, who is for dividing, and so destroying; and is what is the joy of Gospel ministers, and what they labour at and strive for, and which is another reason of the apostle's conflict:

and unto all riches of the full assurance of understanding;
that is, spiritual knowledge and understanding, or the understanding of spiritual things; for the understanding of things natural and civil is not designed; nor a mere notional knowledge of spiritual things, which persons may have, and yet not charity, or love, with which this is here joined; and such an one also, which is sure and certain: for as there is such a thing as the assurance of faith, and the assurance of hope, so likewise of understanding of the Gospel, and the truths of it; concerning which there ought to be no doubt, being to be received upon the credit of a divine testimony: moreover, such a knowledge and understanding of divine things is intended, as is large and abundant, signified by "all riches"; for though it is not complete and perfect in this life, yet it takes a vast compass, and reaches to all the deep things of God; to whatever relates to the person and grace of Christ; to all the things of the Spirit of God; to all the blessings and promises of the covenant of grace; to the riches both of grace and glory, to the things of time and eternity, and which is more clearly explained by the following clause:

to the acknowledgment of the mystery of God, and of the Father, and
of Christ;
that is, to a greater and more perfect knowledge, approbation, and confession of the Gospel, which he had in the preceding chapter called the mystery; see ( Colossians 1:26 Colossians 1:27 ) , and here "the mystery of God", which he is both the author and subject of: it is by him as the efficient cause, ordained by him, and hid in him before the world was; and it is of him, as the subject matter of it; not as the God of nature and providence, which the works of both declare; but as the God of all grace, as God in Christ, which is the peculiar discovery of the Gospel: and "of" him as "the Father" of Christ, which is not discoverable by the light of nature, nor known by natural reason, but is a point of divine revelation; and "of" him as the Father of his people by adoption; and of all his grace, in election to grace and glory; in predestination to sonship, and in the council and covenant of grace; in the scheme of salvation and redemption; in the mission of his Son, and the gift of him as a Saviour and Redeemer. The copulative "and" before "the Father", is left out in the Vulgate Latin, Syriac, and Arabic versions, which read "the mystery of God the Father"; and with it, it may be rendered, as it sometimes is, God, "even the Father": though the word "God" may be considered essentially, and as after distinguished into two of the persons of the Godhead; "the Father" the first person, so called, in relation to his Son, which is no small part of the mystery of the Gospel; and "Christ" the second person, who is equally God with the Father; and the Spirit, who, though not mentioned, is not excluded from this adorable mystery: and which is the mystery "of Christ", he being both the efficient cause and the subject matter of it; it treats of his deity and personality; of his offices, as Mediator, prophet, priest, and King; of his incarnation and redemption; of his grace, righteousness, sacrifice, and satisfaction; of justification by him, pardon through him, and acceptance in him.