Albert Barnes on Matthew 26:51

One of them which were with Jesus. John informs us that this was Peter. The other evangelists concealed the name, probably because they wrote while Peter was living, and it might have endangered Peter to have it known.

And drew his sword. The apostles were not commonly armed. On this occasion they had provided two swords, Lk 22:38. In seasons of danger, when travelling through the country, they were under the necessity of providing means of defending themselves against the robbers that infested the country. This will account for their having any swords in their possession. Lk 10:30. These swords, Josephus informs us, the people were accustomed to carry under their garments, as they went up to Jerusalem.

A servant of the High Priest's. His name, John informs us, was Malchus. Luke adds, that Jesus touched the ear, and healed it; thus showing his benevolence to his foes when they sought his life, and giving them proof that they were attacking Him that was sent from heaven.