God had chosen Joshua to be Moses' successor as far back as the battle with Amalek. In the Book of Numbers God had instructed Moses to ordain Joshua, and in the final chapters of Deuteronomy Moses gave a final word of blessing and encouragement to him. Joshua must have been greatly encouraged to know that he was called of God, for he had a tremendous task before him.
In chapter 2 the two spies are sent out by Joshua, and thus begins the covenant with Rahab. The "line of scarlet thread" mentioned in verse 18 is very significant. It speaks of the precious blood of Calvary, for scarlet is the color of Calvary. Nothing can hurt the soul that has put the precious blood of Christ between it and alarm or danger.
The scarlet thread was the means of salvation to the spies. By it they were let down to the ground and saved from death. The thread (or cord) must have been strong. So the blood of Christ avails, not only for us, but for all who shelter with us in the household of faith; and for others who find it the means of life as they receive it from our hands. Each of us should do as Rahab did. Gather father and mother, brethren and friends to share with us the shelter and safeguard of the precious blood.
It was not the scarlet thread alone that saved Rahab and her family. Behind it was God's oath spoken through the spies, as well as Rahab's faith. The true safety of that house on the wall stood in the moral attitude of one woman in it. Rahab believed God, who had dried up the water of the Red Sea, and who was God in heaven above and in earth beneath. This faith raised her afterwards from her life of shame to become the ancestress of Christ (see Matthew 1:5).
It is interesting to note that of the thousands of people who lived in Jericho, we are told the name of only one of them-- Rahab.
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