What do you want to know about why Jesus asked the disciples to carry a sword along, to protect themselves after he would have been arrested?
What do you want to know about SELF-DEFENSE?
Answer: As at when he was arrested, Jesus could command a legion of angels at a wave of a hand- he did not need to carry a sword with him.
The disciples, on the other hand, as at then, did not have that much spiritual power- they needed a weapon to defend themselves.

But not to use it to cut off someone’s ear when it was their master that was being arrested.
If someone attacks you, then you will use your gun or sword to defend yourself. If you have spiritual power, better, you should use it to cut them down immediately. (2Kings 1:9-14)
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And if God asks you to lay down your weapon, and allow yourself to be used and abused and martyred, THEN YOU WILL OBEY HIM NO MATTER WHAT WEAPON OR SPIRITUAL POWER YOU CARRY. Martyrs lay down their lives willingly.
But if God has not asked you to do so, you MUST kill anyone who attacks you, but only in SELF-DEFENSE! We are at WAR!!
[Usually, Jesus/your guardian angels will respond on your behalf, anyway.]
In no place in the New Testament did God ask any believer to go on the offensive killing people (when we are not Jihadists). We never attack people with our spiritual power or simply because we are angry/emotional. But if you attack us, you will be destroyed INSTANTLY.
You can try. 😃
TURNING THE OTHER CHEEK
But if we are not at war and an unbeliever who does not know Christ randomly slaps me on the street, for example, I can turn the other cheek in love, to show them the love of Christ in hope that they will repent and not be destroyed in the Lake of fire.
But if we are at war and you attack me…you will regret it INSTANTLY. 😂