This can be stated in positive form. AT: "You must treat all widows and fatherless children fairly" (See: [[rc://en/ta/man/translate/figs-doublenegatives]])
To be killed "with the sword" is a metonym that means a person will die violently, or perhaps fighting in a war. AT: "you will die a violent death" (See: [[rc://en/ta/man/translate/figs-metonymy]])