It becomes us not to dogmatize with confidence, but to speak with modesty on a theme so high and difficult. We would suggest that the petition is that ye may be so filled with the Holy Spirit and with all his gifts and graces, as God is filled. This is expressed in a mandatory form by Christ (Matt. 5:48), "Be ye also perfect as your heavenly Father is perfect." Something more than initial Christian life is here prayed for by Paul in behalf of the church in Ephesus. The new birth begins with the love of God in the heart, shed abroad by the Holy Spirit. But such a heart is narrow and needs enlargement; it has remaining defilements which need cleansing. So there are steps and intervals between spiritual infancy and manhood. The crowning act of this process of development is here denoted by the being filled with all the fullness of God. Elsewhere it is expressed by the prayer, "The God of peace himself sanctified you wholly." — 1 Thess. 5:23, (R. V.) Both the filling and the sanctifying are in grammatical forms which imply singleness of action, however long the preparation may have been.
— Half-Hours with St. Paul and Other Bible Readings Chapter 4.