The ruling on not clarifying the truth due to necessity, then clarifying it afterwards

The questioner: If there is a visitor with the teacher, who is an outsider from the Khawarij and whose belief is defective, what is our position?
It is possible that if he fears that if he clarifies the truth they will expel him, he should state what is in the book when the supervisor is present,And he says: saying, "The author of the book said so and so," attributing it to the book, and then, in the supervisor's absence, he should speak the truth.