Imam al-Sadiq (AS) was asked by Muhammad b. Muslim about the situation of a man who becomes ritually impure (mujnib) during his journey, and has nothing but snow or ice at his disposal [and therefore cannot perform the obligatory bath to purify himself]. Imam (AS) replied, 'This is a situation of primary necessity, and I do not think that he should ever return to such a place where his religion is at stake.