The men said to her, Our life for yours, if you don't utter this our business; and it shall be, when Yahweh gives us the land, that we will deal kindly and truly with you.
The two spies did attach one condition to their promise, that being, that under no circumstance would the woman betray their mission  (Joshua 2:14).  Also, there was the agreement that the identity of Rahab's house would be indicated by the red cord.