Albert Barnes Commentary Joshua 2:14

"And the men said unto her, Our life for yours, if ye utter not this our business; and it shall be, when Jehovah giveth us the land, that we will deal kindly and truly with thee." — Joshua 2:14 (ASV)

Our life for yours - See the margin. This is a form of oath, in which God is in effect invoked to punish them with death if they did not perform their promise to save Rahab’s life. Compare the more common form of oath, 1 Samuel 1:26, etc.