Theophylact of Ohrid

But the fervent Peter receives a rebuke, because he used his zeal contrary to the Lord's intention. Whereas the others ask, "shall we strike?" he does not wait for approval (as everywhere he was fervent for the Teacher!), but strikes "the servant of the high priest" and cuts off his "right ear." This happened not by chance, but as a sign that the high priests of that time had all become slaves and had lost their right hearing. For if they had listened to Moses, they would not have crucified the Lord of glory (John 5:46).

Commentary on Luke ↗

Augustine of Hippo

He who struck, according to John, was Peter, but he whom he struck was called Malchus.

Catena Aurea by Aquinas ↗

Ambrose of Milan

For Peter being well versed in the law, and full of ardent affection, knowing that it was counted righteousness in Phineas that he had killed the sacrilegious persons, struck the High Priest's servant. The Lord in wiping away the bloody wounds, conveyed thereby a divine mystery, namely, that the servant of the prince of this world, not by the condition of His nature but by guilt, should receive a wound on the ear, for that he had not heard the words of wisdom. …

Catena Aurea by Aquinas ↗

Bede

Or that servant is the Jewish people sold by the High Priests to an unlawful obligation, who, by the Passion of our Lord, lost their right ear; that is, the spiritual understanding of the law. And this ear indeed is cut off by Peter's sword, not that he takes away the sense of understanding from those that hear, but manifests it withdrawn by the judgment of God from the careless. But the same right ear in those who among the same people have believed, is restored by the Divine condescension to its former office.

Catena Aurea by Aquinas ↗