John Chrysostom

"For some when they had heard did provoke, howbeit not all that came out of Egypt by Moses: And with whom was He grieved forty years? Was it not with them that had sinned, whose carcasses fell in the wilderness? And to whom sware He that they should not enter into His rest, but to them that believed not? So we see, that they could not enter in because of unbelief." After again repeating the testimony, he adds also the question, which makes the argument clear. …

Homily on Hebrews 6 ↗

Theophylact of Ohrid

Having heard, he says, God's promise — "I will give you the land of Canaan" — they did not believe, and by their unbelief they provoked God to anger. See to it, then, that you also do not be unbelieving in the promises. For hearing alone will not benefit you if you do not also believe. Just as hearing did not benefit them either, but on the contrary, they perished with complete justice precisely because they did not believe the words of God. …

Commentary on Hebrews ↗

Oecumenius

For some, having heard the promises of God, just as we hear them, provoked God to anger through unbelief. For He desires to save them just as He saves those who have heard, and they are of no benefit from merely hearing the promise. Thus, he says, you also will not be fulfilled if you have only heard the preaching, unless you also believe. And that there is a need for faith, from those who heard long ago, but because they did not believe, they perished, is confirmed by the word. …

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

191. – Then when he says, who were they that heard, he explains what he had said about their sin. As if to say: You are made partakers of Christ, if you do not harden your hearts, as they who have heard and yet were rebellious. Was it not all? No, not all; for two, namely, Caleb and Joshua remained and consoled the others. …

Commentary on Hebrews ↗