"Blessed be the LORD my strength, which teacheth my hands to war and my fingers to fight."--Ps. 144:1
Christ told Peter to put up his sword, not throw it away.
Christ told his followers to get them swords if they needed them.
When David was king of Israel as God's people (1077-1037 B.C.E), these had enemies, such as the Philistines, Amalekites, and Edomites in which warfare was permitted by Jehovah God.(1 Sam 13:3; 2 Sam 1:1; 8:13)
Thus, David could write that God "is teaching my hands for warfare."(Ps 18:34) These nations of the land of Canaan, along with others, were to be eradicated, to avoid their false religious beliefs and attitudes from infecting the Israelites like a dangerous plague.(Deut 7:1)
However, upon the arrival of Jesus as the Christ in 29 C.E., no longer were the Israelites at war with these nations. Along with the old Mosaic Law covenant that was to be replaced with a "new covenant" (Luke 22:19, 20; Col 2:14), so was the idea or attitude of fleshly war with God's enemies.
Jesus now said that the one identifying mark of a true Christian would be genuine love, saying to his eleven faithful apostles, that "I am giving you a new commandment, that you love one another....By this all will know that you are my disciples, if you have
love among yourselves."(John 13:35)
Thus, love is the identifying mark of a true Christian. As a result, the apostle Paul wrote that "love does
not work evil to one's neighbor; therefore love is the law's fulfillment".(Rom 13:10)
He further said that "though we walk in the flesh, we do
not wage warfare according to what we are in the flesh. For the
weapons of our warfare are not fleshly, but powerful by God for
overturning strongly entrenched things. For we are overturning reasonings and every lofty thing raised up
against the knowledge of God; and we are bringing every thought into captivity to make it obedient to the Christ."(2 Cor 10:3-5)
The expression "we do not wage warfare" is literally "we are not doing military service.” (Greek,
ou . . . stra·teu·o´me·tha; Latin,
non . . . mi·li·ta´mus) Hence, a true Christian
now wars against "every lofty thing raised up against the knowledge of God", cutting away false religion and exposing it as against God, as Jesus did.(Matt 15:3-9)
In his book
The Decline and Fall of the Roman Empire, Edward Gibbon ( Vol. I, p. 416) says that "While they [the Christians] inculcated the maxims of passive obedience, they
refused to take any active part in the civil administration or the military defence of the empire. . . . It was impossible that the Christians, without renouncing a more sacred duty, could assume the character of soldiers, of magistrates, or of princes."
And of the reason why Jesus told Peter to acquire a sword (Luke 22:36) was in order to fulfill Isaiah 53:12 in which Jesus said, quoting from Isaiah 53:12: "For I tell you that this which is written must be accomplished in me, namely, ' And he was reckoned with lawless ones.' For that which concerns me is having an accomplishment."(Luke 22:37) Verse 38 says that "then they (his apostles) said" "Lord, look ! here are two swords." He said to them: "It is enough."