And she said, Let it be as you say. Then she sent them away, and they went; and she put the bright red cord in the window.
Joshua 2:21
Heb 9:19 For when Moses had given all the rules of the law to the people, he took the blood of goats and young oxen, with water and red wool and hyssop, and put it on the book itself and on all the people
Heb 9:22 And by the law almost all things are made clean with blood, and without blood there is no forgiveness.