Lying

In Joshua chapter 2 Rahab lies to the king of Jericho in order to hide the two Israelite spies. My question is, why is this not considered a sin, even if she was doing it for a noble reason? I believe in Hebrews it even mentions this incident in relation to the faith Rahab had. Would this give Christians some sort of leeway to tell a lie if they have good reasons for it as in this case?

Lying is clearly condemned in the Bible. The modern day people have come up with various arguments to justify some forms of lying. This falls under the banner of situational Ethics. So they use the example of Rahab in the Bible to prove that lying in certain situations is permitted if our intention is good.

One of the things to note is Rahab lying to the soldiers to save the Israelite spies is not intended to be model for us to follow. Rahab is praised for her faith in the book of Hebrews 11:31 and for receiving the spies in peace and not for the sake of her lying. The Bible also says Rahab is a prostitute and that doesn't mean that prostitution is permitted in the Bible. On the basis of this story we cannot conclude that Bible permits some forms of lying.
Rahab's lying is a sin. But we have to understand she didn't have the knowledge of the living God. She did all she could in her abilities in order to save the Israelite spies. She could have chosen a different way of protecting the Israelite spies which would have been commendable. God honors her not for her lying but for her act of faith. Rahab had her weaknesses like all of us but she trusted in God and acted on behalf of God's people. This needs to be the highlighted instead of her lying.

The story of Rahab doesn't give a leeway for Christians to lie even if it is intended with good motives. The Bible does not endorse situational ethics.