Mixing of Lawful Things with others in Something

“Abu ‘ Abd Allah (a.s.), has said that he was asked about eel and fish on roasting bars on fire. He (the Imam) said, ‘Whatever is above the eel can be used for food but not what is below; and if anything has dropped from eel, it must be thrown away.’ He (the Imam) said that he was asked about a spleen on roasting bars with meat and underneath there is bread with al-Judha’b (a kind of sandwich); if what is below can be used for food. He (the Imam) said, ‘Yes, the meat and sandwich can be used for food but the spleen must be thrown away because it has a barrier and nothing drips out of it unless a hole is made in it or a cut, in which case you must not eat the items on which drops have fallen from the spleen. 5 ”

A’immah , ‘Alayhim al-Salam, were asked about a certain amount of wheat on which the fat of pigs has melted. He (the Imam) said, ‘If they can wash it they must do so and use it for food;but if they cannot wash it then they can use it as seed to grow a plantation. 5 ”