John Chrysostom

"Being called," he says, "of God an High Priest after the order of Melchisedech": "Of whom we have many things to say and hard to be uttered or explained." When he was about to proceed to the difference of the Priesthood, he first reproves them, pointing out both that such great condescension was "milk," and that it was because they were children that he dwelt longer on the lowly subject, relating to the flesh, and speaks about Him as about any righteous man. …

Homily on Hebrews 8 ↗

Theophylact of Ohrid

So, perfection is achieved through sufferings. Why then should you be indignant at the misfortunes which perfect you? That is, He not only saved Himself, but also brought salvation to others: and not temporary salvation, such as in wars, but eternal. For whom? – "to those who obey Him." How then are you disobedient and in danger of losing salvation? Do you see that the apostle gave this entire discourse such a form because of the faintheartedness of his listeners? Moreover, observe here also something lofty. …

Commentary on Hebrews ↗

Oecumenius

"And having been made perfected." This then is perfection among men, to attain perfection through sufferings. And he has spoken all things becoming of a man, behold, also becoming of God; "he became the source of eternal salvation for all who obey him." That is, not only was he himself saved, but he also brought salvation to others; and not temporary, derived from wars, but eternal. To whom is this? To those who obey. How then do you disobey and risk falling away from the grace? …

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

260. – Then when he says, and being made perfect he became the source of eternal salvation to all who obey him, he mentions the fruit of His Passion, namely, in Christ and in His members. In Christ the fruit was glorification; hence, he says, and being made perfect, for from the instant of His conception He was perfectly consummated as to the happiness of His soul, inasmuch as it was drawn to God; but he still had a nature that could suffer, although after His Passion He could not suffer. …

Commentary on Hebrews ↗