When we read the story of Rahab in Joshua 2, we are meant to understand that story in light of the exodus backdrop. The scarlet thread recalls the blood of the unblemished lamb. The window in Rahab’s house recalls the doorposts and lintel of an Israelite home. Impending divine judgment was true for both Exodus 12 and Joshua 2. And in both stories, the designated sign meant deliverance for those inside.
Early in the book of Joshua, a Canaanite named Rahab confessed her faith in the God of Israel to some Israelite spies (Josh. 2:8-11). She then asked that she and her household be spared the coming judgment of the conquest (2:12-13).
The spies told her, “Behold, when we come into the land, you shall tie this scarlet cord in the window through which you let us down, and you shall gather into your house your father and mother, your brothers, and all your father’s household” (Josh. 2:18).
So Rahab did. After the men left, she tied the scarlet cord in the window (Josh. 2:21), trusting and waiting.
This scarlet cord was consistently interpreted in the early centuries of Christian interpretation as signifying the cross of the Lord Jesus (see the writings of Justin Martyr, Origen, Augustine, Jerome, Clement, Irenaeus, and Ambrose).
Such an interpretation has caused no small amount of controversy for modern readers. First of all, there’s no clear prophecy in Joshua 2 to the future redemptive work of Jesus. Second, the color-connection of a “scarlet” cord and the red blood of Jesus is not a substantive correspondence. Third, no New Testament author connects the scarlet cord to the cross.
Those three points are valid but not decisive. I’m going to offer a cumulative case that argues for the scarlet cord of Rahab to be a type of Christ’s cross-work. Let’s notice how the episode with Rahab is meant to evoke the event of the exodus.
First, Rahab tells the spies, “For we have heard how the LORD dried up the water of the Red Sea before you when you came out of Egypt…” (Josh. 2:10).