Matt. 26:52 "Put your sword back in its place," Jesus said to him, "for all who draw the sword will die by the sword."
Some would say that this seems to be a strong indictment against war, and place it against certain verses where Jesus seems to advocate fighting.
We'll look at those in a moment, but it should first be noted that this verse is in the form of proverbial wisdom, and is therefore not an advocation of pacifism -- nor, by reason of its proverbial nature, is it absolute, as is obvious since not every single person who has drawn a sword (or other weapon) has died by the same means.
Hence there is neither contradiction of nor relevance to other verses cited as contradictory. Moreover, that this is not intended as a statement in pacificism is seen in that the saying also carries an eschatological overtone that may be seen through this parallel, from an Aramiac Targum on Isaiah 50:11 [Albright's commentary on Matthew, 324]:
Behold, all you that kindle a fire, that take the sword: go, fall into the fire you have kindled, and fall by sword you have taken.
Expressed as this is, it has the meaning that "God's will is being fulfilled and nothing can hinder it." It has nothing to do with whether or not one actually and literally dies by the sword.
Tekton associate Eric Vestrup adds:
I fail to see how having a sword constitutes "living by the sword". The idiom "living by the sword" denotes a life of aggressive violence. How does having a sword necessitate such a life? Why can't one have a weapon for protection. I have friends with firearms, yet they don't live by the gun. In the Lukan passage, note that Jesus addresses the disciples to buy a sword if they lacked one. One can reasonably suppose that Jesus is here using a figure of speech, for when the disciples took His words in the wrong fashion, producing but two swords, Jesus tells them that the two swords are sufficient.
If Jesus was here telling them to live by the sword, it would be unreasonable to think that a scant two swords would suffice for a group of at least eleven men. In the Matthean passage Jesus is most clear about promulgating what one thinks is the Christian cause by using force -- He corrects the disciples' mistaken notion that the cause would be furthered by their preventing His arrest. The Lukan passage has nothing at all to do with the Matthean passage.
What about verses cited in opposition? Let's have a look:
Matt. 10:34 "Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword."
There are a few problems with using this verse against 26:52. For one thing, it is clear that "sword" here is a figurative reference to personal division, not to literal weaponry.
Skeptics may reply that it doesn't matter, for any cause of division or strife is in opposition to Jesus' supposed pacificism, and as one critic puts it, Jesus "has seeded extreme division, sedition and enmity wherever Christianity is promulgated" by "exhorting his followers to violence."
Perhaps the critics need to look at the verses previous to these to see just who it is Jesus is saying will be prone to violence:
Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves. But beware of men: for they will deliver you up to the councils, and they will scourge you in their synagogues; And ye shall be brought before governors and kings for my sake, for a testimony against them and the Gentiles. But when they deliver you up, take no thought how or what ye shall speak: for it shall be given you in that same hour what ye shall speak. For it is not ye that speak, but the Spirit of your Father which speaketh in you. And the brother shall deliver up the brother to death, and the father the child: and the children shall rise up against their parents, and cause them to be put to death. And ye shall be hated of all men for my name's sake: but he that endureth to the end shall be saved. But when they persecute you in this city, flee ye into another: for verily I say unto you, Ye shall not have gone over the cities of Israel, till the Son of man be come. The disciple is not above his master, nor the servant above his lord. It is enough for the disciple that he be as his master, and the servant as his lord. If they have called the master of the house Beelzebub, how much more shall they call them of his household? Fear them not therefore: for there is nothing covered, that shall not be revealed; and hid, that shall not be known. What I tell you in darkness, that speak ye in light: and what ye hear in the ear, that preach ye upon the housetops. And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell. Are not two sparrows sold for a farthing? and one of them shall not fall on the ground without your Father. But the very hairs of your head are all numbered. Fear ye not therefore, ye are of more value than many sparrows. Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven. But whosoever shall deny me before men, him will I also deny before my Father which is in heaven. (Matthew 10:16-33)
Far from advocating violence, Jesus is here predicting that Christians will become the victims of violence: It is the persecutors who wield the sword and become the foes. In other words, Jesus is saying here what we have: Religion will become an excuse for inhumanity. The critics have the sentiments precisely backwards.
Luke 22:36 He said to them, "But now if you have a purse, take it, and also a bag; and if you don't have a sword, sell your cloak and buy one."
An advocation of war? Some even think that Jesus equipped his followers with swords in anticipation of trouble, and note that Peter scuffled with the Temple police to aid in resisting Jesus' arrest. That's an overstated case: The passage in Luke refers to only TWO swords - and during the so-called "scuffle," there was nothing but Peter slicing off a servant's ear, followed by Jesus instructing Peter to put his sword away. Raymond Brown [Death of the Messiah, 689] has rightly admonished those who read military intent into this passage:
...such an isolated instance of spontaneous defense that could have occurred in a melee of any period is scarcely indicative of belonging to a resistance movement.
The swords in question, at any rate, were not the longswords of our medieval television programs. This would most likely have been a Jewish short sword - a dagger used as protection against wild animals and robbers, considered so essential that even the "peace-loving Essenes" carried it, and it was permitted to be carried on the Sabbath as part of one's adornment. [See Hengel, Was Jesus a Revolutionist?, 21] Needless to say, this weapon would not be much use against the Temple police - much less against any number of armed Roman soldiers.
John 14:27 Peace I leave with you, my peace I give unto you: not as the world giveth, give I unto you. Let not your heart be troubled, neither let it be afraid.
You might see this one cited too -- though within the context of John 14, this is clearly "peace" in a spiritual sense and has nothing to do with physical warfare. The word "peace" here is eirene, and can mean peace, prosperity, quietness, or rest, as in Matt. 10:13: "And if the house be worthy, let your peace come upon it: but if it be not worthy, let your peace return to you." Obviously this is not "peace" in the sense of the opposite of fighting and war.
For more on this subject, see here.