Mat 26:52 Put up again you sword into its place: for all they that take the sword shall perish with the sword.
Alternative: Return your sword into its place because all who take the sword are destroyed by the sword.

While this sounds simply like an expression of pacifism and perhaps the idea of karma, it is much more if we understand how Christ sees the world and its conflicts. Christ says explicitly that his larger purpose is not to bring peace but the sword in Mat 10:34. For him, the sword was a symbol of struggle. It is the opposite of the cup, which is the symbol of acceptance. Christ makes this context explicit in Jhn 18:11.

Christ sees the world as having an inherent conflict between the temporal and the eternal, the worldly and the spiritual. This struggle is necessary and healthy. Christ doesn't say "throw away your sword." He say, "Put your sword in its place." Swords have a place and the physical struggle that they represent also has a place. However, acceptance also has its place. The secret is understanding the nature of the situation we are in and what must happen so we can satisfy what God expects from us.

Why was this situation one of acceptance? Christ has already said that he is accepting God's will. Others may not realize what his happening. He asks Judas, Why are you here? because Judas and the others do not realize that they are all playing their parts in a larger drama. Christ understand that to win this particular conflict, he must give up the physical, accepting physical death so that the spirit and his teachings can triumph.

Does this mean that the sword has no place in the world? Christ accepts its role in the world in the same way that he accepts the role of money. They are necessary.

Update:
In thinking about the previous verse, I realized that Christ was saying something hidden in his statement about those who take up the sword will die by the sword. Think for a moment: Did any of his followers take up the sword? No, they did not start an armed rebellion, either against the Jewish leaders or Rome. But how did they die? All of his followers died by the sword in one form or another. They died at the hands of others exerting physical power over them. So, his followers DIDN'T take up the sword and yet they died by the sword.

So was Christ wrong? If we assume that his statement means that those who do not take up the sword will not die by the sword, we are wrong. He doesn't say that. We have to understand exactly what he was saying. He was saying that philosophies that teach people that might makes right will eventually die because all physical power is temporary (like physical life).

Though his followers died by the sword, their ideas did not. Their ideas grew more and more powerful. Symbolically, the sword is physical power. Ideas are the power of ideas. Physical power can only defeat the ideas when those ideas are based on physical power. Ideas can destroy a physical power, as Rome was eventually destroyed, but a physical power cannot destroy ideas.

"Put up again" is from apostrephô (apostrepho), which means "to turn back," "to turn aside," "to dissuade from," "to bring back," and "to recall."

"Sword" is machaira (machaira), which means a "large knife," "large dagger," "short sword," or "dirk." It specifically the type of weapon used for making sacrifices, by assassins, bodyguards, and jugglers.

"Take" is from lambanô (lambano) which means "to take," "to receive," "to apprehend with the senses," and "to seize." It is also specifically used to mean seized with emotion.

"Perish" is from apollumi, which is a very strong form of "to destroy," "to kill," "to slay," and "to lose." It is translated as "lost" and "perish" elsewhere in Matthew. It means "to destroy utterly." It also means "to ruin" a woman.