it’s

Do not denude me without reason ~~ ~~ Do not wield me without valor

so cipheramnesia is looking even more in the correct direction

I find the OP interesting because of the parallels in Western stereotypes of Samurai mores (I can’t speak for how these stereotypes play out in Japan).

There’s an idea in the West that Bushido demands that a drawn sword must be bloodied before it can be re-sheathed. If there’s any accuracy in this, it’d be a nice parallel to the Chivalry’s “do not draw me without reason,” but with an interesting difference in cultural perspective. They both boil down to, “think twice before drawing your sword in anger.”