John Chrysostom

"Of whom," he says, "we have many things to say and hard to be explained, seeing ye are dull of hearing." Because they do not hear, the doctrine is "hard to be explained." For when one has to do with men who do not go along with him nor mind the things that are spoken, he cannot well explain the subject to them. But perhaps some one of you that stand here, is puzzled, and thinks it a hard case, that owing to the Hebrews, he himself is hindered from hearing the more perfect doctrines. …

Homily on Hebrews 8 ↗

Theophylact of Ohrid

Intending to speak about the superiority of Christ's priesthood, he rebukes his listeners in advance, pointing out that because of their infancy he spoke such lowly things about Christ and occupied himself with teaching about the flesh of Christ. For if they had not been weak, he would long ago have reminded them of loftier things. …

Commentary on Hebrews ↗

Oecumenius

"Concerning this Christ, there is much to say and it is hard to explain." He says it is because of you, that you are sluggish, and you do not grasp the more perfect things about Him. For having spoken so many humble things about the incarnation, he wished to move on to the divine matters. Therefore, because of your cause, he says, that you are sluggish and do not allow for the perfect things, the word concerning how Christ is a high priest according to the order of Melchizedek is hard to explain. …

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

262. – Then (v. 11) he prepares the souls of his hearers for what is to follow. In regard to this he does two things: first, he shows their slowness; secondly, his intention (chap. 6). In regard to the first he does two things: first, he shows the importance of what is to be said; secondly, their slowness to understand (v. 11b). 263. – He says, therefore: Thus I have said that He was called a high priest: About this we have much to say: 'Hear, for I will speak of great things' (Pr. 8:6). …

Commentary on Hebrews ↗