In certain situations, the Bible commands us to be shrewd. Rebekah with Jacob is a timeless example. The Bible commands us to be shrewd towards evil, in emergencies, and when something is about to go down wrong. If you want to have success against evil, you will need to become shrewd. You must have the ability to outthink your enemy. Christianity is not a competition about who has the best ethics. It is about furthering the kingdom of God in the face of evil.