Beitzah 4 - And Beit Shammai was lenient
Rabbi Eliezer was the student of Beit Shammai, and he quoted the following opinion about the egg laid on a Holiday: it is permitted to eat it, and even its mother hen.
Now let's analyze this. If the hen is kept for food - then of course it is permitted, and Rabbi Eliezer is not telling us anything new. And if it is kept for laying eggs, then it should be forbidden!? - We are dealing with a special situation where someone bought a hen and did not tell us why he bought it. If later we see that he takes that hen to slaughter, we know that both the hen and the egg were designated for food. However, this explanation leads us to the analysis of the idea of retroactive designation, so let's try another one.
Another explanation of Rabbi Eliezer's statement is that it is simply an "exaggeration," or special emphasis. He just wanted to emphasize that the egg can be eaten, so he included even the mother hen and said, "Everything can be eaten!" - even though the second part of the statement is obvious. He did say something similar on another occasion: "The egg may be eaten, and its mother, and the chick, and its shell." Obviously, the shell is not edible. And if you want to say that he meant, "Chick in a shell" - that nobody allows. We see then, that it was said just to make the point.
Art: Two hens by (after) Adriaen Van Utrecht