And through this chain of transmission from Muhammad ibn Ya‘qub, from a group of our companions, from Ahmad ibn Muhammad, from Ali ibn Ahmad, who raised it (the narration) from Abu ‘Abdullah عليه السلام: I asked Imam عليه السلام about a person afflicted with smallpox who experienced janabah. Imam عليه السلام said: "If he became impure due to intercourse (intentional), then he must perform ghusl (ritual bathing), but if it was due to a nocturnal emission (ihtilam), then he should perform tayammum (dry ablution).”"