“…let him who has no sword sell his sword and buy one.”
Those who desire to somehow negate Jesus’ direct teachings and commands concerning non-resistance, present Luke 22:36 as some kind of proof text to somehow override all His direct commands and lifestyle living on the subject. Although the passage can be somewhat confusing as to why the Lord tells them all to buy a sword and then says two are enough, He makes it very clear as to the purpose of the need for a sword. Two swords for the twelve (who normally went out in twos) are hardly enough for defense against robbers, protecting the innocent, and nowhere near enough to be an attacking army or to be the knights in shining armor which some say Jesus is asking us to be. On the other hand, one knife was enough for Peter to commit the criminal act of slicing off an ear (v.50).
In the next verse the Lord clearly states the purpose of needing a sword, “For I tell you, that this which is written must be fulfilled in Me, ‘And He was classed among criminals’; for that which refers to Me has its fulfillment.” (v.37). From there they proceeded to the Garden where Peter subsequently used his knife to commit a criminal act. Although throughout His ministry the Lord associated with sinners, there is no record that “He was classed among criminals”, until now when one of His close disciples commits a violent criminal act. The Lord then immediately rebukes Peter for his action and tells him to put up his knife and saying, “For those who live by the sword will die by the sword” (Matt.26:52). Soon after He is telling Pilate “My kingdom is not of this world. If my kingdom were of this world, then my servants would be fighting”. (Jn.18:36).
So, why have I referred to a knife in the above, when our English Bible renders the Greek word sword. The English translators have chosen to translate both Greek words Machaira and rhomphaia as sword. Yet note the difference according to Strongs:
4501 rhomphaía – a long Thracian sword; "a sword, scimitar" (Souter). 4501 (rhomphaía) is "a large, broad sword" that both cuts and pierces – an imposing sword, synonymous with finality (dominance). Rev. 1:16
We find that 3162 (machaira) is primarily used throughout the New Testament, and 4501 (rhomphaia) is exclusively used in Revelation and figuratively in Luke 2:35. Of course it makes total sense that Peter and another were not carrying a large broad battle sword, as it would likely have been illegal, and of course the Lord would not have had to ask if they had one as it would have been clearly visible. The 3162 machaira, on the other hand, is defined as a slaughter-knife, much like what we would call a butcher or hunting knife. Of course the same knife could be used in battle or self-defense, as Jesus used the word in that context when He said those who live by it will die by it. The Lord Himself stated His purpose for being sure that Peter had such a knife on his person (v.37), and then rebuked him for using it in self-defense (Matt. 26:52).
The Wikipedia article entitled Makaira, further describes this knife as defined in ancient Greece:
“Homer mentions the makhaira, but as a domestic knife of no great size. In period texts, μάχαιρα has a variety of meanings, and can refer to virtually any knife or sword (taking the meaning of today's Greek μαχαίρι), even a surgeon's scalpel, but in a martial context it frequently refers to a type of one-edged sword; a sword designed primarily to cut rather than thrust.” (Wikipedia)
It would have been difficult to make such a tool of a person’s trade illegal, even with the Roman fears of insurrection. Surely fishermen, butchers, tanners, shepherds, and many agrarian tradesmen would routinely carry the makaira, and according to the Wikipedia article above, a surgeon would carry a makaira. This type of knife could also have been routinely used as the Rabbi and His disciples prepared their meals during their travels. Therefore it would be entirely posible that Peter the fisherman was carrying such a knife, which was obviously easily concealed, as the Lord at least alluded that He didn’t know Peter carried one. Of course Andrew, James and John were also fishermen, and there was only one other knife in the group that day.
We don’t know who held the other knife, but we could have expected James and John may have lashed out, as our Lord rebuked them earlier in the ministry for wanting to call down fire on the inhospitable Samartan town. We might have also expected this reaction from the one called Simon the Zealot, but apparently Peter was the one who fulfilled the prophecy of being the criminal in the group.
Also of interest, is that after the infilling of the Holy Spirit, there is never a record of this rebuked Peter, nor the rebuked James and John, nor any of the apostles or early disciples ever advocating, approving, or participating in physical self-defense or insurrections.
The bottom line is, Jesus telling them to buy a sword, is not a not a scriptural justification for any kind of violence.