“I once asked abu ‘Abd Allah (a.s.), about the case of a man who enters the wilderness and finds different eggs which he does not know from what kind of birds they are; if it is of birds that are undesirable or of the desirable ones. He (the Imam) said, ‘There is knowledge in it which is not unclear. If you look at each egg you can find which end is the head and which end is the bottom in which case you can eat; but if you cannot distinguish the shape of one end from the other, then leave it.’”