She believes Yahweh is real and will act against Jericho. In this she was no different than most in Jericho, for she tells the spies that they were all quaking with fear. The difference is that she switches sides. She tells the truth, reveals the secret, of this fear to the spies, when she didn’t have to. This is the act of faith. Telling the truth to Israel, and deceiving those at war with Israel and her God. Identifying with Israel, and not with her own people. Like Ruth, she did something questionable on the surface as an act of faith, and was therefore rescued from her judged people and brought into the kingdom of Israel. “He has delivered us from the power of darkness and conveyed us into the kingdom of the Son of His love” (Colossians 1:13).
By faith Rahab hid the spies and deceived the Jericho police. Her faith took action. So should our faith.
We are pilgrims in a strange land like Rahab. Many act surprised and indignant when the culture is biased against Christians. This does not fit at all with the apostles' reaction (Acts 5:40-41, for one example). Rahab risked worse than this, and acted for Israel, anyway. Expect opposition and ridicule. Don’t let it deter you from doing what is right.
The scarlet cord
This brings Passover to mind, of course. Israel came out of Egypt, seeing a red strand over their houses. They come into Canaan seeing a red strand over the house of a believer. In Passover, Israel was to gather and stay in the house, to be safe from judgment. Noah called people into the ark to be safe, but none came, except his own family. Lot called his family out of Sodom to be safe, but the only ones who came fell away.
Rahab’s reward, and ours
This must have been a surprise to find any believers in Canaan, but the spies, Joshua, and Rahab’s future husband all respond in the same way: acceptance. She lives with Israel “to this day” (Josh 6:25). She marries Salmon (Matt 1:4), son of Nahshon, who was the leader of Judah in Numbers 7:12. She is not just accepted in a “tolerate the second-class immigrant” kind of way! From her comes David, and later Jesus. Like Rahab, we are not just forgiven our past sin. We are favored greatly by the King, and set at His table to eat as royalty. God's promise to Abraham is coming true: nations and kings will come from you.