Joshua 2:12

True token, such a one as, when I shew it to the Israelites, they may preserve me and mine. She is not content with a verbal promise, she requires something permanent and sensible, as a mark of their mutual engagements, (Calmet) a token of their sincerity. They afterwards appointed a piece of scarlet to be hung out of the house, where those were to be collected who should be entitled to protection. Rahab was bound not to divulge their secret, nor to betray them. If she had instructed others of her fellow-citizens to hand out the same mark, she would have forfeited all her privileges, ver. 20. (Haydock)