“This scarlet cord in the window”
unless, when we enter the land, you have tied this scarlet cord in the window through which you let us down, and unless you have brought your father and mother and brothers and all your family into your house. (Joshua 2:18 BSB)
What it sounds like today
A practical signal so the soldiers know which house to skip.
The cultural key
On the surface the scarlet cord is a simple identifying marker, but its color and function deliberately echo the Passover. Just as the Israelites in Egypt daubed lamb's blood on their doorframes so the destroyer would 'pass over' those houses, Rahab ties a scarlet (blood-red) cord in her window so that when Israel destroys Jericho, everyone inside her house is spared. A red sign displayed on the dwelling means the household under it is safe from the coming judgment. The parallel marks Rahab's rescue as a kind of Passover for a Canaanite: a foreigner, and a prostitute, is delivered because she trusted the God of Israel and displayed the sign of faith. She is later honored in Hebrews' roll call of faith and appears in Matthew's genealogy of Jesus. A modern reader sees a practical flag; the first hearers heard the blood-red sign of Passover salvation extended to an outsider.
Recovered meaning
Rahab's scarlet cord echoes the Passover blood on the doorposts: a red sign in the window means this household is spared the coming judgment. A Canaanite prostitute is saved by faith and grafted into Israel and the line of Jesus.