These comments come from Paul E. Kretzmann’s commentary on Ephesians 3:14-19. The commentaries can be found on KretzmannProject.org.
“This idea is developed still further: That Christ may dwell through faith in your hearts. Not only the gifts and virtues of Christ, but the exalted Christ personally lives in the hearts of His believers, Gal. 2, 20. There is the most intimate, the most happy communion between Christ and the Christians, begun in conversion, but in need of daily growth and strengthening, for it is through faith that Christ dwells in the heart, and the loss of faith in the forgiveness of sins means the loss of Christ Himself. If Christ does not live in us, grow in us, day after day, His power will soon diminish and His picture fade away. But with Christ in the heart, there is steady progress: That you, firmly rooted and grounded in love, be fully able to comprehend with all the saints what the breadth and the length and the depth and the height is. Love is the proof and test of faith. If Christ lives in the heart by faith, then love toward God and love toward one’s neighbor will follow as a matter of course. And with the growth of faith in the form of firm confidence, love will also take a firmer hold on the Christian; it will be set as solidly as a root takes hold of the ground from which it derives strength and life. Thus the condition is obtained which enables the believer fully to understand, to get a mental grasp of, what is the breadth and length and height and depth. ALL the saints should have this understanding, all the believers should grow in Christian knowledge. And in the connection in which the apostle here writes, he undoubtedly has in mind the Church with its immense dimensions. This building extends over the entire world from North to South, from East to West, through all periods of time until the last day; it includes the believers that are now sleeping in their graves, and reaches to the heavens, where its exalted Ruler sits at the right hand of God. The Church embraces the fullness of the elect, not only of Israel, but also of the Gentile world – a poor, small crew in the sight of men, but a mighty assembly before the omniscient eye of God.
And finally, Paul prays for the Christians that they might be strengthened: To know the love of Christ, which passeth knowledge, the knowledge-surpassing love of Christ, that you may be filled up to all the fullness of God. It is an incomprehensible, indescribable, immeasurable love by which Christ has founded the Church, by which He builds and extends it, a love which overcomes the hardest hearts, which influences even the greatest criminals, and always with the aim of building up the Church. This love is beyond the capacity of the human mind and intelligence, but the enlightened Christian will be able to get at least some idea of its extent and power, of its miraculous power in gaining lost sinners for Christ and the Church. And with the growth in this knowledge the hope and prayer of the apostle will finally be fulfilled, namely, that the Christians will be filled unto all the fullness of God, that this goal may be reached in them. It is a fullness of grace possessed and bestowed by God, the full measure of His gracious gifts to which the apostle has reference. Upon this measureless source the believers draw, increasing daily in virtues and blessings, as vessels of God’s mercy; themselves the possessors of boundless love and expending freely therefrom to the praise and honor of God. Though this ideal fail of full realization in this life, it is worth striving for with untiring energy.”