It was asked of Imam Jafar ibn Muhammad Al-Sadiq عليه السلام was asked about a man with smallpox who became junub (ritually impure due to sexual discharge). Imam عليه السلام said: 'If he became junub (through intercourse), he should perform ghusl, but if he had a nocturnal emission (i.e., he experienced it while sleeping), he should perform tayammum.'.
