5 “Then Simon Peter, having a sword, drew it, and smote the high priest's servant, and cut off his right ear. And the servant's name was Malchus.” This is the only evangelist who has given us the very name of this servant, as Luke is the only one who tells us that the Lord touched his ear and healed him. The interpretation of Malchus is, one who is destined to reign. What, then, is signified by the ear that was cut off in the Lord's behalf, and healed by the Lord, but the renewed hearing that has been pruned of its oldness, that it may henceforth be in the newness of the spirit, and not in the oldness of the letter? Who can doubt that he, who had such a thing done for him by Christ, was yet destined to reign with Christ?
And his being found as a servant, pertains also to that oldness that genders to bondage, which is Agar. But when healing came, liberty also was shadowed forth. Peter's deed, however, was disapproved of by the Lord, and He prevented Him from proceeding further by the words: “Put up your sword into the sheath: the cup which my Father has given me, shall I not drink it?” For in such a deed that disciple only sought to defend his Master, without any thought of what it was intended to signify.
And he had therefore to be exhorted to the exercise of patience, and the event itself to be recorded as an exercise of understanding. But when He says that the cup of suffering was given Him by the Father, we have precisely the same truth as that which was uttered by the apostle: “If God be for us, who can be against us? He that spared not His own Son, but gave Him up for us all.” But the originator of this cup is also one with Him who drank it; and hence the same apostle likewise says, “Christ loved us, and gave Himself for us an offering and a sacrifice to God of a sweet-smelling savor.”
Source: Tractates on the Gospel of John (New Advent)