Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing. Of whom we have many things to say - The words περι οὑ, which we translate of whom, are variously applied:
1. To Melchisedec;
2. To Christ;
3. To the endless priesthood.
Those who understand the place of Melchisedec, suppose that it is in reference to this that the apostle resumes the subject in the seventh chapter, where much more is said on this subject, though not very difficult of comprehension; and indeed it is not to be supposed that the Hebrews could be more capable of understanding the subject when the apostle wrote the seventh chapter than they were when, a few hours before, he had written the fifth. It is more likely, therefore, that the words are to be understood as meaning Jesus, or that endless priesthood, of which he was a little before speaking, and which is a subject that carnal Christians cannot easily comprehend.
Hard to be uttered - Δυσερμηνευτος· Difficult to be interpreted, because Melchisedec was a typical person. Or if it refer to the priesthood of Christ, that is still more difficult to be explained, as it implies, not only his being constituted a priest after this typical order, but his paying down the ransom for the sins of the whole world; and his satisfying the Divine justice by this sacrifice, but also thereby opening the kingdom of heaven to all believers, and giving the whole world an entrance to the holy of holies by his blood.
Dull of hearing - Νωθροι ταις ακοαις· Your souls do not keep pace with the doctrines and exhortations delivered to you. As νωθρος signifies a person who walks heavily and makes little speed, it is here elegantly applied to those who are called to the Christian race, have the road laid down plain before them, how to proceed specified, and the blessings to be obtained enumerated, and yet make no exertions to get on, but are always learning, and never able to come to the full knowledge of the truth.