John Chrysostom

This he says of every man, that as he that is dead is henceforth freed from sinning, lying as a dead body, so must he that has come up from baptism, since he has died there once for all, remain ever dead to sin. If then thou hast died in baptism, remain dead, for any one that dies can sin no more; but if thou sinnest, thou marrest God's gift. After requiring of us then heroism of this degree, he presently brings in the crown also.

Homily on Romans 11 ↗

Theophylact of Ohrid

"For he who has died has been freed from sin." This he says of the whole man. As "he who has died has been freed from sin," that is, has been delivered, is free, so also you, who have been baptized and have died to sin, remain dead.

Commentary on Romans ↗

Irenaeus

Wherefore also He drove him out of Paradise, and removed him far from the tree of life, not because He envied him the tree of life, as some venture to assert, but because He pitied him, [and did not desire] that he should continue a sinner for ever, nor that the sin which surrounded him should be immortal, and evil interminable and irremediable. …

Against Heresies Book III ↗

Thomas Aquinas

Then when he says, for he that is dead, he clarifies what he had said: first, in regard to the first effect; second, in regard to the second, at now, if we be dead. In regard to the first it should be noted that the assemblage of sins is destroyed when a man has his sins remitted. So he clarifies how the body of sin is destroyed when he says, he that is dead to sin through baptism, in which we die together with Christ, is justified from sin, i.e., transferred to the state of justice: and such were some of you. …

Commentary on Romans ↗