Here is another instance of Jesus teaching us to be shrewd, like the dishonest manager :
Luke 16:8 NASB "And his master praised the unrighteous manager because he had acted shrewdly; for the sons of this age are more shrewd in relation to their own kind than the sons of light.
The point is that we are not of this world but we are in this world. We should expect to be the target of sharp practice, because that is the way of the world, but we should not let it affect our ministry.
In the case of the shrewd manager, he was au courant, aware of his future dilemma and made arrangements to tackle it. Christians should be aware that they will be hearing God's voice, and should not be like Ananias and Sapphira:
Hebrews 4:7 NASB God again designated a certain day as "Today," when a long time later He spoke through David as was just stated: "Today, if you hear His voice, do not harden your hearts."
Of course, you should ensure you are under the proper Covenant, which most Christians unfortunately are not.
Due diligence, people.