Ambrose of Milan

But how remarkable is the humility of the divine that the Lord of heaven did not scorn to visit the servant of a centurion! Faith shines forth in works, but humanity operates more in emotions. He certainly did not do this because he could not care for him in his absence, but to give you a form to imitate in humility, by teaching you to be submissive to those who are lower and deferential to those who are higher. …

Commentary on Luke ↗

Bede

And when those who had been sent returned home, they found the servant, who had been sick, well. The faith of the master is proven, and the health of the servant is restored. Therefore, the merit of the Lord can also benefit the servants, not only by the merit of faith but also by the zeal of discipline. Matthew explains this more fully when the Lord said to the centurion: Go, and let it be done for you as you have believed (Matthew 8), and the boy was healed from that hour. …

On the Gospel of Luke ↗

Bonaventure

As to the swiftness of the desired healing, there is added: And those who had been sent returned, as if with hope of salvation obtained through the word of Christ, which he spoke, which Matthew expresses, although Luke is silent: "As you have believed, let it be done for you. …

Commentary on Luke, Chapter 7 ↗