It is thought that this action of Peter's was before the apprehension of our Saviour, though after the discovery of it, as our evangelist reports it; because upon the apprehension of our Saviour, both Matthew 26:56, and Mark 14:50, agree, that the disciples fled; and it can hardly be thought that if Peter had seen his Master apprehended he would have adventured upon so daring and provocative an action; nor could Christ, had he been first bound, have stretched out his hand, to have touched his ear, and healed it. Lest any should wonder how Peter came by a sword, we may read, Luke 22:38, that the disciples had two swords amongst them, probably brought out of Galilee for the defence of themselves and their Master against assaults from robbers in that long journey.
Related Commentaries of John 18:10
John 18:10
10 Then Simon Peter having a sword drew it, and smote the high priest's servant, and cut off his right ear. The servant's name was Malchus.