An unlikely arrangement

In this passage, Rahab and the spies enter into a covenant together. They make an oath one to another.
This is most unlikely. That a Gentile woman and 2 Jewish men would make this type of arrangement. Not only the participants are unique, but the criteria of the covenant is also quite unlikely. That a scarlet thread would be the token of life and death, both for the spies and for Rahab and her family.