A.T. Robertson Commentary John 18:10

"Simon Peter therefore having a sword drew it, and struck the high priest`s servant, and cut off his right ear. Now the servant`s name was Malchus." — John 18:10 (ASV)

Having a sword (εχων μαχαιραν). It was unlawful to carry a weapon on a feast-day, but Peter had become alarmed at Christ's words about his peril. They had two swords or knives in the possession of the eleven according to Luke (22:38). After the treacherous kiss of Judas (on the hand or the cheek?) the disciples asked: "Lord, shall we smite with the sword?" (Luke 22:49). Apparently before Jesus could answer Peter with his usual impulsiveness jerked out (ειλκυσεν, first aorist active indicative of ελκυω for which see 6:44) his sword and cut off the right ear of Malchus (John 18:10), a servant of the high priest. Peter missed the man's head as he swerved to his left. Luke also (Luke 22:50) mentions the detail of the right ear, but John alone mentions the man's name and Peter's. There was peril to Peter in his rash act as comes out later (John 18:26), but he was dead long before John wrote his Gospel as was Lazarus of whom John could also safely write (12:9-11). For ωταριον, diminutive of ους, see Mr 14:47 (only other N.T. example), another diminutive ωτιον in Mt 26:51 (Luke 22:51).