Live by the sword, die by the sword

51 And behold, one of those who were with Jesus stretched out his hand and drew his sword and struck the servant of the high priest and cut off his ear. 52 Then Jesus said to him, “Put your sword back into its place. For all who take the sword will perish by the sword. 53 Do you think that I cannot appeal to my Father, and he will at once send me more than twelve legions of angels? 54 But how then should the Scriptures be fulfilled, that it must be so?” (Mt 26:51-54).

That's a stock pacifist prooftext. But is that what it means?

i) For staters, there's an insurmountable obstacle to the pacifist interpretation. If Jesus disapproved of his disciples bearing arms, then why did he permit them to bear arms? After all, for the course of three years, they'd been on the road together for weeks or months at a time. They did everything together. 

Was Jesus so unobservant that he never noticed that some of his disciples had swords? Indeed, the very passage in question presumes that one or more of his disciples were in possession of a sword. And that wouldn't be unusual. Due to bandits, travelers were often armed. 

If Jesus didn't approve, would we not expect him to forbid his disciples to bear arms? Why did he not command them to disarm? 

Moreover, even assuming he was too inattentive to notice that some of his disciples were armed, on the night of his arrest, he knew that his disciples had swords. Why did he not order them to discard their swords? 

The pacifist interpretation makes Jesus look like a bumbler or terribly ineffectual. 

ii) V52 has a proverbial ring. Like proverbs generally, it isn't meant to be universally true. Not everyone who resorts to violence dies a violent death. In fact, that may not even be true in the majority of cases. 

It is true that people who live by violence are at greater risk of suffering violence in return. However, that's not necessarily what the aphorism is meant to convey.

iii) Pacifists say this reflects the radical teaching of Jesus. However, the statement itself isn't especially novel. You have variations on that statement in prior Jewish literature. For instance, Jer 15:2 says "those who are for the sword, to the sword" (cf. 43:11). Likewise, a Targum of Is 50:11 says those grasp the sword will fall on the sword. And the OT uses different metaphors to make the same point:

He makes a pit, digging it out,
and falls into the hole that he has made.

(Ps 7:15)

Whoever digs a pit will fall into it,
and a stone will come back on him who starts it rolling.

(Prov 26:27; cf. Eccl 10:8).

iv) However, the ultimate derivation of Jesus's aphorism may be Gen 9:6. His statement seems to be a paraphrase of that seminal verse:

For all who take the sword 

will perish by the sword.

Whoever sheds the blood of man,
by man shall his blood be shed.

Notice the formal and conceptual similarities: the balanced, contrasting parallelism; the theme of poetic justice. 

Although Genesis uses the same "bloodshed" language in both clauses, these are not morally equivalent actions. In the first clause, bloodshed refers to forbidden killing (murder). In the second clause, bloodshed refers to obligatory killing (judicial execution). 

It's quite possible Mt 26:52 has the same connotation. Peter's intervention to defend Christ is wrongful violence.