Theophylact of Ohrid

The leper was prudent and believed; therefore he did not say: if You ask God; but believing in Him as God, he said: "if You will." Christ touches him as a sign that nothing is unclean. The Law forbade touching a leper as unclean; but the Savior, wishing to show that nothing is unclean by nature, that the requirements of the Law must be abolished, and that they have power only over men, touches the leper — whereas even Elisha so feared the Law that he did not even wish to see Naaman, who was leprous and asking for healing.

Commentary on Mark ↗

Augustine of Hippo

Mark puts together circumstances, from which one may infer that he is the same as that one whom Matthew (Matt. 8:2) relates to have been cleansed, when the Lord came down from the mount, after the sermon.

Catena Aurea by Aquinas ↗

Bede

And because the Lord said that He came not to destroy the Law but to fulfill, (Matt. 5:17) he who was excluded by the Law, inferring that he was cleansed by the power of the Lord, showed that that grace, which could wash away the stain of the leper, was not from the Law, but over the Law. And truly, as in the Lord authoritative power, so in him the constancy of faith is shewn; for there follows, Lord, if thou wilt, thou canst make me clean. …

Catena Aurea by Aquinas ↗