The Scarlet Thread of Faith: The Oath to Rahab Text: Joshua 2:15-21
Introduction: A Covenant on the Wall
The story of Rahab is a glorious disruption in the middle of a conquest. Here we have the armies of the living God, poised to execute His righteous judgment against the Canaanites, a people whose cup of iniquity was full to the brim. And right on the edge of that judgment, on the very wall of the city marked for utter destruction, God makes a spectacular display of His sovereign grace. He plucks a brand from the burning. And not just any brand, but a prostitute, a Gentile, a woman of Jericho.
This is not a sentimental story about a girl with a heart of gold. This is a story about the nature of true faith, the binding power of covenant oaths, and the bloody thread of redemption that runs from the beginning of the world to the end. Rahab is not saved because she was a good person who made a few bad choices. Rahab is saved because she heard the reports of what God had done, and she believed them. She feared the true God more than she feared the king of Jericho. Her faith was not a vague, pious sentiment; it was a concrete, active, life-altering conviction. As James tells us, she was justified by works, which is to say, her works proved that her faith was the genuine article (James 2:25).
In our passage today, we see the outworking of that faith. It is not enough for the spies to simply escape. A covenant must be made. An oath must be sworn. Terms must be established. This is how God deals with His people. He does not save us into a vague relationship of fuzzy feelings. He saves us into a covenant, a solemn bond with blessings and curses attached. What we see here, with Rahab and the spies, is a microcosm of God's covenant dealings with all His people. It is a picture of salvation, sealed with an oath, and marked by a sign.
We live in a time that despises oaths. We want all our commitments to be provisional, all our relationships to be fluid. We want to keep our options open. But God does not keep His options open. He binds Himself by His Word, and He calls us to do the same. This scene is a lesson in the grammar of salvation, a salvation that is secured by a promise and identified by a blood-red sign.
The Text
Then she let them down by a rope through the window, for her house was on the city wall, so that she was living on the wall. And she said to them, “Go to the hill country, lest the pursuers reach you. And hide yourselves there for three days until the pursuers return. Then afterward you may go on your way.” And the men said to her, “We shall be free from this oath to you which you have made us swear, unless, when we come into the land, you tie this cord of scarlet thread in the window through which you let us down, and gather to yourself into the house your father and your mother and your brothers and all your father’s household. And it will be that anyone who goes out of the doors of your house into the street, his blood shall be on his own head, and we shall be free; but anyone who is with you in the house, his blood shall be on our head if a hand is laid on him. But if you tell this business of ours, then we shall be free from the oath which you have made us swear.” And she said, “According to your words, so be it.” So she sent them away, and they went; and she tied the scarlet cord in the window.
(Joshua 2:15-21 LSB)
Escape and Instruction (v. 15-16)
We begin with the practical outworking of Rahab's faith. She takes action.
"Then she let them down by a rope through the window, for her house was on the city wall, so that she was living on the wall. And she said to them, 'Go to the hill country, lest the pursuers reach you. And hide yourselves there for three days until the pursuers return. Then afterward you may go on your way.'" (Joshua 2:15-16)
Notice the details. Her house is on the wall, which is both a place of great vulnerability and, in this case, the very instrument of deliverance. This is how God works. He uses the ordinary, the mundane, the very geography of our lives, to accomplish His extraordinary purposes. The wall was meant to keep the Israelites out, but God uses it as the exit ramp for His servants and the entry point for His grace to Rahab.
Rahab does not just provide the means of escape; she provides the strategy. She is thinking clearly under immense pressure. Her counsel is wise and prudent: "Go to the hill country." Go the opposite direction from where they expect you to go. Wait for three days. This is not a faith that sits back and waits for a miracle; it is a faith that acts in wisdom. True faith does not make us fools. It makes us shrewd. We are to be wise as serpents and innocent as doves. Rahab demonstrates both. She has thrown her lot in with Israel and their God, and she is now actively working for their success, which has become her success.
The Terms of the Covenant (v. 17-20)
The spies now formalize the agreement. Faith has been professed, and works have followed. Now the covenant must be defined with precision.
"And the men said to her, 'We shall be free from this oath to you which you have made us swear, unless, when we come into the land, you tie this cord of scarlet thread in the window through which you let us down, and gather to yourself into the house your father and your mother and your brothers and all your father’s household.'" (Joshua 2:17-18)
An oath is a solemn act of religious worship. It is calling God to witness a promise and to judge the one who swears if he breaks it. The spies understand the gravity of this. They are binding not just themselves, but all of Israel, before God. And so, they lay out the conditions. Oaths are not blank checks. They have stipulations. Their obligation has a corresponding obligation on her part.
The central condition is the sign: "tie this cord of scarlet thread in the window." This is not an arbitrary marker. In Scripture, scarlet is the color of blood, sacrifice, and redemption. This cord is a clear echo of the blood of the Passover lamb painted on the doorposts and lintels in Egypt. On that night, the angel of death passed over every house marked by the blood. Here, the army of judgment will pass over the house marked by the scarlet thread. It is a sign of faith, pointing to a bloody substitution. Rahab is being instructed to place her trust not in her own merit, but in the sign of deliverance God has provided. This is a gospel ordinance in the middle of Jericho.
The second condition is to gather her family. This is federal salvation. Rahab, as the head of her household in this matter, the believing head, becomes the means of deliverance for her entire family. They must be gathered under the sign. This is the principle of the household covenant we see throughout Scripture. Noah enters the ark, and his family with him. Abraham is circumcised, and his household with him. The Philippian jailer believes, and he and his entire household are baptized. Salvation is personal, but it is never individualistic. Faith in a family has corporate implications.
"And it will be that anyone who goes out of the doors of your house into the street, his blood shall be on his own head, and we shall be free; but anyone who is with you in the house, his blood shall be on our head if a hand is laid on him. But if you tell this business of ours, then we shall be free from the oath which you have made us swear." (Joshua 2:19-20)
The boundaries of the covenant are made sharp and clear. Inside the house, under the sign, there is safety. Outside the house, there is judgment. There is no middle ground. To leave the safety of the house is to reject the terms of the covenant and to place oneself outside the sphere of its protection. Their blood would be on their own heads. This is a terrifying and necessary principle. God's grace has boundaries. To be saved, you must remain within the ark of His provision, within the household of faith.
The spies are putting their own lives on the line for anyone inside that house. "His blood shall be on our head." This is the language of covenant substitution. They are taking responsibility. But there is also a condition of silence. "If you tell this business of ours..." Secrecy is required. This is a military operation, but it is also a test of her loyalty. Is she truly with them, or is she hedging her bets?
The Obedience of Faith (v. 21)
Rahab's response is simple, immediate, and complete.
"And she said, 'According to your words, so be it.' So she sent them away, and they went; and she tied the scarlet cord in the window." (Joshua 2:21)
"According to your words, so be it." This is the language of submission and faith. It is the echo of Mary's response to the angel: "Behold, the bondslave of the Lord; may it be done to me according to your word." Rahab accepts all the terms. She does not argue or negotiate. She receives the word of salvation and she acts on it.
And notice her immediacy. She does not wait until she hears the trumpets of the Israelite army. She does not procrastinate. "She tied the scarlet cord in the window." As soon as the spies are gone, the sign goes up. This is the mark of a living faith. It does not delay obedience. Her house is now marked. For days, that scarlet cord hung from her window, a silent testimony of her treason to Jericho and her allegiance to the God of Israel. It was a public declaration of her faith, visible to all who passed by. She was not ashamed of the sign of her salvation.
The Cord of Christ
This entire account is dripping with the gospel. We must see the typology here, for the Old Testament is the gospel in pictures, and this is one of the clearest portraits we have.
We, like Rahab, are citizens of a city that is under a sentence of divine judgment. The whole world lies under the wrath of God. We are by nature children of wrath, living on the wall of a doomed city. There is no escape through our own efforts or our own righteousness. We are all, in our own way, harlots, having sold ourselves to other loyalties.
But God, in His mercy, sends messengers, heralds of the gospel, who come into our doomed world. And by grace, some of us hear the report of God's mighty acts, of His victory over sin and death at the cross and the empty tomb. And like Rahab, we are brought to a holy fear and a true faith. We confess that Jesus is Lord and that our old king, the prince of this world, has no real claim on us.
And what are we told to do? We are told to lay hold of the promise of salvation. This salvation is not a vague hope; it is a covenant, sealed with an oath. God has sworn by Himself that all who trust in His Son will be saved. And this covenant has a sign, a scarlet thread that runs through all of history. That thread is the blood of Jesus Christ.
We are commanded to display this sign. We are to tie the scarlet cord of Christ's blood over our lives and over our homes. We do this when we are baptized into His name, when we come to His table, when we confess with our mouths that Jesus is Lord. Our faith must be visible. It cannot be a secret we keep in our hearts. It must be a banner we hang from the window for all the world to see.
And we are to gather our households under this sign. We are to bring our children, our families, into the ark of safety. We are to instruct them in the terms of the covenant and warn them that outside of Christ and His church, there is only judgment. His blood is on our head for our families if we fail to bring them with us into the house of faith. And we must stay in the house. We must persevere in the faith, abiding in Christ, remaining within the covenant community where His grace is administered.
Rahab the harlot was saved by grace through faith. Her name is listed in the great hall of faith in Hebrews 11. She is found in the genealogy of the Lord Jesus Christ Himself. The scarlet thread in her window was a testimony to her faith in the promise, and that faith was counted to her as righteousness. And that same grace, that same bloody cord of redemption, is held out to us today. Let us, like Rahab, say "According to your words, so be it," and tie the sign of our salvation to the window of our lives, without delay and without shame.