In the wake of religious riots in Egypt, the emperor Decius decreed that all subjects of the Empire must actively seek to benefit the state through witnessed and certified sacrifice to "ancestral gods" or suffer a penalty: only Jews were exempt. Decius' edict appealed to whatever common mos maiores might reunite a politically and socially fractured Empire and its multitude of cults; no ancestral gods were specified by name. The fulfillment of sacrificial obligation by loyal subjects would define them and their gods as Roman. Roman oaths of loyalty were traditionally collective; the Decian oath has been interpreted as a design to root out individual subversives and suppress their cults, but apostasy was sought, rather than capital punishment. A year after its due deadline, the edict expired.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What religious group was exempt from sacrifices?
Jews