Then Joshua son of Nun secretly sent two spies from Shittim. “Go, look over the land,” he said, “especially Jericho.” So they went and entered the house of a prostitute named Rahab and stayed there. Joshua 2:1 NIV

Before the spies lay down for the night, she went up on the roof and said to them, “I know that the Lord has given you this land and that a great fear of you has fallen on us, so that all who live in this country are melting in fear because of you. We have heard how the Lord dried up the water of the Red Sea for you when you came out of Egypt, and what you did to Sihon and Og, the two kings of the Amorites east of the Jordan, whom you completely destroyed. When we heard of it, our hearts melted in fear and everyone’s courage failed because of you, for the Lord your God is God in heaven above and on the earth below. “Now then, please swear to me by the Lord that you will show kindness to my family, because I have shown kindness to you. Give me a sure sign that you will spare the lives of my father and mother, my brothers and sisters, and all who belong to them—and that you will save us from death.” Joshua 2:8-13 NIV

Now the men had said to her, “This oath you made us swear will not be binding on us 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, your brothers and all your family into your house. If any of them go outside your house into the street, their blood will be on their own heads; we will not be responsible. As for those who are in the house with you, their blood will be on our head if a hand is laid on them. But if you tell what we are doing, we will be released from the oath you made us swear.” “Agreed,” she replied. “Let it be as you say.” Joshua 2:17-21 NIV