John Gill emphasizes the importance of growing in grace and knowledge of our Lord and Savior Jesus Christ, highlighting that spiritual growth is a gradual process akin to the growth of a seed. He explains that while believers should be thankful for their gifts, they are encouraged to seek an increase in grace through prayer, the Word, and reflection on God's promises. Gill notes that growth in grace leads to increased faith, hope, love, and humility, which are essential for preserving oneself and others from error. He concludes with a doxology, attributing glory to Christ for His divine attributes and the grace bestowed upon believers both now and forever.

Ver. 18. But grow in grace,.... In the gifts of grace, which, under a divine blessing, may be increased by using them: gifts neglected decrease, but stirred up and used, are improved and increase. And though men are to be thankful for their gifts, and be contented with them, yet they may lawfully desire more, and in the use of means seek an increase of them, which may be a means of preserving themselves, and others, from the error of the wicked. Moreover, by "grace" may be meant internal grace. The work of grace is gradual; it is like a grain of mustard seed, or like seed cast into the earth, which springs up, it is not known how, first the blade, then the ear, then the full corn in the ear; saints are first babes, and from children they grow to young men, and from young men to fathers. There is such a thing as growth in grace, in this sense; every grace, as to its act and exercise, is capable of growing and increasing; faith may grow exceedingly, hope abound, love increase, and patience have its perfect work, and saints may grow more humble, holy, and self-denying: this is indeed God's work, to cause them to grow, and it is owing to his grace; yet saint, should show a concern for this, and make use of means which God owns and blesses for this purpose, such as prayer, attending on the word, and looking over the promises of God, for an increase of faith; recollecting past experiences, and looking to the death and resurrection of Christ for the encouragement of hope, and to the love of God and Christ, for the stirring up of love to both, and to the saints; considering the sufferings of Christ, the desert of sin, and the glories of another world, to promote patience and self-denial, and the pattern of Christ, to excite to humility; though "grace" may also intend the Gospel, the knowledge of which is imperfect, and may be increased in the use of means, and which is a special preservative against error, a growth in which saints should be concerned for: and [in] the knowledge of our Lord and Saviour Jesus Christ; of his person, office, and grace, than which nothing is more valuable, and is to be preferred to everything; it is the principal thing in grace, and is the beginning and pledge of eternal life, and will issue in it; for an increase of which, and a growth in it, the word and ordinances are designed; and nothing can be a greater security against error than an experimental growing knowledge of Christ. The Syriac version adds, "and of God the Father"; and so some copies read: to him [be] glory, both now, and for ever; or "to the day of eternity"; that is, to Christ, who is truly God, or otherwise such a doxology would not belong to him, be ascribed the glory of deity, of all divine perfections; the glory of all his offices and work as Mediator; the glory of man's salvation; and the glory of all that grace, and the growth of it, together with the knowledge of himself, which saints have from him; and that both in this world, and that which is to come. Amen; so be it.