John Chrysostom

But it is necessary also to unfold the history, to make the argument more clear. For when they had come forth out of Egypt, and had accomplished a long journey, and had received innumerable proofs of the power of God, both in Egypt, and in the Red Sea, and in the wilderness, they determined to send spies to search out the nature of the land; and these went and returned, admiring indeed the country, and saying that it abounded in noble fruits, nevertheless it was a country of strong and invincible men: and the ungrateful and senseless …

Homily on Hebrews 6 ↗

Theophylact of Ohrid

Having spoken about hope and about the need to await with confidence the reward and rest there from the labors here, he next proves on the basis of the prophet's words: believers will enter into rest, but unbelievers will not enter, just as the ancients did not enter. For after the Israelites crossed the Red Sea and received in the wilderness countless proofs of God's care for them and His power, they resolved to send spies to examine the nature of the land they intended to enter. …

Commentary on Hebrews ↗

Oecumenius

Saying that it is necessary to hope for good things from Christ, he now says that we must not harden our hearts towards this faith and hope, so that we do not suffer the same things as those who, in the desert, became unbelievers. And today, which is always evident, as if he were saying: Whenever and as long as today is, if you hear the voice of the one calling Christ, do not harden your hearts and become stubborn so as not to hear him. …

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

170. – Having proved that Christ is greater than Moses, the Apostle now concludes that Christ is more deserving of our obedience. He does this by the authority of David the prophet in Psalm 94. He does three things: first, he proposes the authority which contains an exhortation; secondly, he explains it (v. 12); thirdly, he argues from the authority and the explanation (chap. 4). …

Commentary on Hebrews ↗