John Calvin Commentary Luke 22:51

"But Jesus answered and said, Suffer ye [them] thus far. And he touched his ear, and healed him." — Luke 22:51 (ASV)

And having touched his ear, he healed him. By his foolish zeal, Peter had brought severe discredit upon his Master and his doctrine, and there can be no doubt that this was a scheme by which Satan attempted to involve the Gospel in eternal disgrace, as if Christ had kept company with assassins and seditious persons for revolutionary purposes. This, I think, was the reason why Christ healed the wound Peter had inflicted.

But a terrible and astonishing stupidity must have seized his adversaries, who were not at all affected by seeing such a miracle. And yet, it is less surprising that they did not see the power of Christ displayed in the person of another when, after having themselves been knocked to the ground by his voice, they still continued to rage (John 18:6). Such is the spirit of delusion by which Satan drives the reprobate mad when the Lord has handed them over to blindness.

Above all, in the man himself who was healed, there is a striking example of ingratitude. For neither did the divine power of Christ subdue him to repentance for his hardness, nor was he overcome by kindness so as to be changed from an enemy into a disciple. For it is a foolish notion of the monks that he was also healed in his soul, so that the work of Christ might not be left incomplete; as if God's goodness is not poured out daily on those who are unworthy.