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. Having a sword - See the note on Luke 22:36.
Cut off his right ear - He probably designed to have cloven his scull in two, but God turned it aside, and only permitted the ear to be taken off; and this he would not have suffered, but only that he might have the opportunity of giving them a most striking proof of his Divinity in working an astonishing miracle on the occasion: see the notes on Matthew 26:51-56 (note).
The other three evangelists mention this transaction; but neither give the name of Peter nor of Malchus, probably because both persons were alive when they wrote; but it is likely both had been long dead before St. John published his history.