John Gill Commentary Joshua 2:20

"But if thou utter this our business, then we shall be guiltless of thine oath which thou hast made us to swear." — Joshua 2:20 (ASV)

And if you utter this our business
So that others would either hang out scarlet threads or get into her house for shelter, (See Gill on Joshua 2:14);

then we will be quit of your oath which you have made us to swear ;
be under no obligation to make it good, by saving her and her father's house.