John Chrysostom

The body then is indifferent between vice and virtue, as also instruments (or arms) are. But either effect is wrought by him that useth it. As if a soldier fighting in his country's behalf, and a robber who was arming against the inhabitants, had the same weapons for defence. For the fault is not laid to the suit of armor, but to those that use it to an ill end. And this one may say of the flesh too which becomes this or that owing to the mind's decision, not owing to its own nature. …

Homily on Romans 11 ↗

Theophylact of Ohrid

Where are the Manicheans who say that the body is sinful by nature? The body is an instrument, and an instrument is a means for both virtue and vice. Thus a sword serves the warrior as a weapon for the defense of citizens, while for a robber it is a weapon against citizens. "Do not present your members to sin as instruments of unrighteousness." For whoever sins acts unjustly often toward his neighbor, and always toward himself. …

Commentary on Romans ↗

Thomas Aquinas

Then when he says, so as to obey, he clarifies this admonition. In regard to this it should be noted that sin reigns in man in two ways: in one way, through internal consent of the mind. To remove this he says, so as to obey the lusts thereof. For it is by obeying the passions of sin with our minds that sin reigns in us: go not after your lusts (Sir 18:30). In a second way sin reigns in us through the performance of the act. …

Commentary on Romans ↗