Then she let them down by a cord through the window: for her house was upon the town-wall, and she dwelt upon the wall. And she said to them, Depart to the mountain, lest the pursuers meet you; and hide yourselves there three days, until the pursuers have returned: and afterward ye may go your way. And the men said to her, We will be blameless of this thy oath which thou hast made us swear. Behold, when we come into the land, thou shalt bind this line of scarlet thread in the window by which thou didst let us down: and thou shalt bring thy father, and thy mother, and thy brethren, and all thy father’s household home to thee. And it shall be, that whoever shall go out of the doors of thy house into the street, his blood shall be upon his head, and we will be guiltless: and whoever shall be with thee in the house, his blood shall be on our head, if any hand be upon him. And if thou shalt utter this our business, then we will be quit of thy oath which thou hast made us to swear. And she said, According to your words, so be it. And she sent them away, and they departed: and she bound the scarlet line in the window. (Joshua 2:15-21, Webster)

upon her request, the way of Salvation was immediately made clear and plain to her; it was a very simple way; all she had to do was to hang a piece of scarlet cloth [thread] in the window; a child could do that; as well, Salvation presently from the Wrath to come is equally simple; trusting in the Lord Jesus Christ, and in His Precious Blood, secures eternal Salvation. The assurance of Salvation to Rahab was not built upon an inward experience, but rather upon an outward evidence; that is, the scarlet line. In it was perfection; in herself imperfection.

Looking upon that “true token” and believing the testimony respecting it, she was assured of deliverance in the Day of Doom that was coming. Thus, the outward token gave an inward peace. The Believer in Jesus enjoys a similar peace. The preciousness of Christ’s Blood, and the Testimony of the Holy Scriptures concerning it, is the outward token which brings assurance of Salvation to the heart that trusts Christ. It was vain for Rahab to seek for Salvation upon the ground of personal worthiness; for she was vile indeed. It is equally vain for the most moral to claim Salvation today, for all have sinned, none are righteous, and all are under sentence of death as seen in Romans 5:12.

The condition was that the red cord would hang from the window, and that all must stay in the house where the window was. To leave the house would leave its protection. Safety was guaranteed for all who remained in the house, destruction for all who left the house. It is the same with the Blood of Christ, which the scarlet thread represented.
As long as we remain in the house of safety provided by the Blood, we are safe. To leave this house of safety, which is Faith in Christ and Him Crucified, guarantees destruction.

Rahab lost not a moment in making her calling and election sure. She bound the scarlet thread in the window; and as directly she did so, she was saved, that is, she was in safety, and assured of safety. Prior to binding the scarlet line in the window, she was ordained to destruction, but, from the moment she trusted that “true token,” she was ordained to Salvation, as well as all her family, provided they stayed in the house, which means that they placed their trust in the scarlet thread as well.
Rahab’s story proves how simple, yet how very powerful, faith is. It doesn’t depend on our worthiness but on the mercy of Christ. When we trust in what Jesus has done; His sacrifice on the Cross, we rest in the assurance that we are safe from judgment. Faith is as simple as Rahab’s act: believe, obey, and stay under the covering of the Blood. Just as Rahab’s family found refuge behind the scarlet cord, our peace and safety are found in Christ alone.