5:11-14 Dull hearers make the preaching of the gospel difficult, and even those who have some faith may be dull hearers, and slow to believe. Much is looked for from those to whom much is given. To be unskilful, denotes want of experience in the things of the gospel. Christian experience is a spiritual sense, taste, or relish of the goodness, sweetness, and excellence of the truths of the gospel. And no tongue can express the satisfaction which the soul receives, from a sense of Divine goodness, grace, and love to it in Christ.
12. for the time—considering the long time that you have been Christians. Therefore this Epistle was not one of those written early.
which be the first principles—Greek, "the rudiments of the beginning of." A Pauline phrase (see on Ga 4:3; Ga 4:9). Ye need not only to be taught the first elements, but also "which they be." They are therefore enumerated Heb 6:1, 2 [Bengel]. Alford translates, "That someone teach you the rudiments"; but the position of the Greek, "tina," inclines me to take it interrogatively, "which," as English Version, Syriac, Vulgate, &c.
of the oracles of God—namely, of the Old Testament: instead of seeing Christ as the end of the Old Testament Scripture, they were relapsing towards Judaism, so as not only not to be capable of understanding the typical reference to Christ of such an Old Testament personage as Melchisedec, but even much more elementary references.
are become—through indolence.
milk … not … strong meat—"Milk" refers to such fundamental first principles as he enumerates in Heb 6:1, 2. The solid meat, or food, is not absolutely necessary for preserving life, but is so for acquiring greater strength. Especially in the case of the Hebrews, who were much given to allegorical interpretations of their law, which they so much venerated, the application of the Old Testament types, to Christ and His High Priesthood, was calculated much to strengthen them in the Christian faith [Limborch].