John Chrysostom

The best Physicians after they have made a deep incision, and have increased the pains by the wound, soothing the afflicted part, and giving rest and refreshment to the disturbed soul, proceed not to make a second incision, but rather soothe that which has been made with gentle remedies, and such as are suited to remove the violence of the pain. …

Homily on Hebrews 21 ↗

Theophylact of Ohrid

So we were not speaking in vain when we said that the words "Vengeance is Mine" he introduces in a veiled manner for their consolation. For behold, now he speaks more clearly with them, persuading them not to lose patience. So, he says, do not imitate anyone else, but yourselves. At the beginning of your faith you struggled; always remember this struggle, so that through carelessness you do not lose what you previously attained through struggle. …

Commentary on Hebrews ↗

Oecumenius

"Remember the earlier days." Behold, he speaks to them more plainly, urging them not to lose patience. He says, therefore: Do not imitate others, but imitate yourselves. For at the beginning of your faith you struggled; keep this struggle in mind; do not lose what you have achieved through laziness. Behold the cleverness; shaking their souls with the memory of that fire, he now encourages them with praises. "after being illuminated." Either concerning baptism, he says, they are illuminated, or concerning the knowledge of Christ.

The Pseudo-Oecumenian Catena on Hebrews ↗

Thomas Aquinas

536. – After exhorting them by frightening reasons to cling to Christ by faith, hope and charity, the Apostle now gives pleasing reasons, as a good physician after cutting applies soothing lotions. For of all commendations for doing good, there is one which best stimulates a person to persevere in a good work already begun. For virtue praised acquires an immense drive, and glory is a strong stimulus. …

Commentary on Hebrews ↗