Maybe we’ve translated it incorrectly?
But, in a day and age in which context has been skewed and now everyone is connected to everywhere… context can be lost on us.
Some point to the Strong’s concordance in this instance stating that it doesn’t even recognize the noun “sword” in Luke 22:36. Making an underlying implication in that Jesus wasn’t saying to purchase it as a weapon but as more of a utility device for basic necessities such as cooking, and eating.
But, Seeing Christ’s reference here is that of Isaiah 53:1, and the context of this particular verse, saying, “For I tell you that this Scripture must be fulfilled in me: ‘And he was numbered with the transgressors.’ For what is written about me has its fulfillment.” (Luke 22:37 ESV), it seems evident in that he most likely was not referring to a cooking or eating utensil only.
Zooming out, we see him telling the disciples about the cost of following him; that they’ll be sent out like sheep among wolves, that they must be as shrewd as snakes.
The typical use of this word “μάχαιρα” is derived from the root word μάχη, which is an adjective meaning “to battle” or “to fight.”
Rudolf Bultmann unpacks this quite well in “Theology of the New Testament, Volume 1.”