"So she let them down by a rope through the window, for the house she lived in was part of the city wall. She said to them, 'Go to the hills so the pursuers will not find you. Hide yourselves there three days until they return, and then go on your way.'" NIV translation
Rahab let the men out of the city without letting anyone know about them. She also told them to go in the opposite direction of the men that were out searching for them. In the three days that they were to stay there, we see a picture of the fact that Jesus would be raised from the dead in three days. The spies were as good as dead if they had been caught but, at the end of three days, the men would have given up and their lives would be saved.
"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.'" NIV translation
There were two additional responsibilities that Rahab had in order for her and her family to be saved.
First, she had to tie a red cord to the window that she had let the spies out through. This was a marker for the men to identify the house when they came back into the city. It reminds us of the fact that there is only one way to be saved and that is through the blood of Jesus Christ.
The second thing that she had to do was to get all of her family into her house. This is an important fact in that many people think that, since their mom or dad have been a part of the church for years, they are as well. But, as we see it was not their relationship with Rahab that was going to save them, but their location (being in her 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.'" NIV translation
Rahab could only tell her family to come in and stay but she could not tell them about the spies and their deal. This reminds us that it is by faith that we are saved through grace. Her family would have to believe her and trust that she was looking out for them. Faith is an individual thing and we cannot be saved through another's faith.
In this, we see the fact that we, as Christians, do not have the power to save anyone. We can tell them how to be saved (accepting Jesus Christ) but everyone has to make their own choice. We are to share the gospel with those around us but, if they refuse the blood of Jesus, then, they must pay for their sins with their own blood.