If someone asks me for an answer during a test, can I tell him the wrong answer? (Response to follow-up question – I prefer not to refuse either to not suffer socially or so the cheater gets what he deserves.)
A person must maintain total integrity in all his dealings – after all, we are
commanded to act like Hashem in all our deeds, and Hashem’s seal is truth (Shabbos
55a). Furthermore, someone who is meticulously honest and truthful will merit
receiving the Presence of the Shechinah.