Character freezes when big hitboxs

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1

When I try to make a big hitbox and I weld it to the character it freezes for a second.
Here is my weld script :

function Combat:Weld(part1, part2, whichOne)
	local weld = Instance.new("WeldConstraint")
	weld.Part0 = part1
	weld.Part1 = part2
	if whichOne == 1 then
		weld.Parent = part1
	else
		weld.Parent = part2
	end
	return weld
end