'Place this salt in water, and then wait on me in the morning.' The son did as he was commanded. The father said to him: 'Bring me the salt, which you placed in the water last night.' The son having looked for it, found it not, for, of course, it was melted.

In plain words: The father tells his son to put salt in water and come back in the morning. When asked to bring the salt back, the son cannot find it, because it has dissolved.