Hebrews 5:11

Of whom we have many things to say
Either of Melchizedek, or of Christ, or of his priesthood or of all of these; since the apostle does largely treat of them in the following chapters: he says many things concerning Melchizedek in the seventh chapter, and many things of Christ, and his priesthood, in those that follow; Christ is a large and inexhaustible subject in the Gospel ministry, and what a Gospel minister delights to dwell on; and it is a fund and stock from whence he is furnished with things of the greatest usefulness, and of the utmost importance:

and hard to be uttered;
as were many things respecting Melchizedek, mentioned in ( Hebrews 7:3 ) and also concerning Christ, and his priesthood: abstruse and difficult things are to be looked into, considered, searched after, and insisted on: the whole Scripture is profitable, and the whole counsel of God is to be declared, and things hard to be explained should be attempted; this is the way to an increase of light and knowledge; though it becomes ministers to consult their own abilities, and the capacity of their hearers, that they do not go beyond them:

seeing ye are dull of hearing;
this dulness of hearing is thought by some to arise from their afflictions; or from their attachment to the law of Moses; or rather from their sluggishness, indocility, and want of industry; and often times this arises from pride and prejudice, and irreverence of the word of God; and frequently from the deceitfulness of riches, and the cares of this life.