Theophylact of Ohrid

The centurion, that is, the commander over a hundred soldiers, seeing that He died so sovereignly, was amazed and confessed. Notice how the order was reversed! The Jews put Him to death, a pagan confesses; the disciples scatter, the women remain.

Commentary on Mark ↗

Augustine of Hippo

This also he most of all wondered at, that after that voice which He sent forth as a figure of our sin, He immediately gave up His spirit. For the spirit of the Mediator showed that no penalty of sin could have had power to cause the death of His flesh; for it did not leave the flesh unwillingly, but as it willed, for it was joined to the Word of God in the unity of person.

Catena Aurea by Aquinas ↗

Bede

But the centurion, who stood opposite, seeing that he had expired in such a way, said: Truly this man was the Son of God. The clear cause of the miracle concerning the centurion is explained: seeing that the Lord had expired in this way, that is, having given up his spirit, he said: Truly this man was the Son of God. For no one has the power to give up the spirit, except he who is the creator of souls. …

On the Gospel of Mark ↗