When you read through the Bible and come across a woman named Rahab, the first thing you learn about her is not the most favorable in the eyes of God. We learn in Joshua 2:1 that she was 
“a harlot.” Why does the Bible choose to tell us that? God could have left that particular detail out and the rest of the story would still remain the same (or so it would seem).
In Joshua 2, we learn something else about this woman–she had a faith in God which she confessed to the spies (2:11) and acted upon (2:12-21; 6:22-25). In fact, she is held up as an example of faith in Hebrews 11:31 and James 2:25. Additionally, there are only five women mentioned in the genealogy of Jesus (in Matthew 1:1-17), and Rahab is one of them (1:5).
So, why did God tell us that Rahab was a harlot? He didn’t do it to scorn her, nor did He do it to justify prostitution. Surely His purpose was to teach us that He is ready to forgive anyone of any sin, if they will truly repent and follow Him! What a much-needed lesson for us to learn!