We discussed this question on Thursday’s daf (58a). Ameimar there teaches that it depends on when the eggs formed. Eggs that formed before the chicken became treifah are not kosher, whereas eggs that formed afterwards are kosher. Rashi explains that the pre-treifah eggs are prohibited because they are halachically considered an extension of the chicken. Regarding the post-treifah eggs, Ameimar explains that since the eggs are a product of something prohibited (the treifah hen) and something permitted (the kosher rooster which fertilized the eggs), the eggs are kosher.
There is a basic question that needs to be answered in order to understand Ameimar’s teaching. Why aren’t the eggs that formed after the chicken became a treifah also prohibited by dint of the fact that they are a halachic extension of the treifah chicken?
The Chazon Ish takes up this issue in his commentary to Yoreh Deah (Siman 14 [II]) and illuminates the way for us. First, the Chazon Ish has us consider the following hypothetical: What if a miracle occurred and an animal deemed treifah survived—would the animal now be kosher? The Chazon Ish brings sources that prove that in such a case the animal would remain non-kosher. Apparently, the Chazon Ish observes, once an animal contracts a treifah condition, the Torah brands it as prohibited for all time. In other words, the Chazon Ish explains, there are two different aspects when it comes to a treifah animal: (1) the mortal defect itself, and (2) the resultant permanent prohibited status.
From the perspective of this new understanding, the Chazon Ish continues, let’s examine the eggs of a treifah chicken. On the one hand, we could argue that since the eggs will emerge from the chicken, they should not be caught up in the treifah injury that has befallen the chicken. So although the Torah pronounced a permanent prohibition upon the chicken itself due to the fatal defect it suffered, this should not apply to the eggs. On the other hand, we could argue that the halachah ought to follow the here-and-now, and since presently the eggs are halachically one with the chicken, they, too, should be swept up in the Torah’s declaration of permanent prohibition as a result of the chicken becoming treifah.
The Chazon Ish explains that the distinction found in our Gemara reflects how Chazal balanced these two arguments. If the eggs were already present during the moment that the chicken was permanently branded as non-kosher as a result of the treifah event, then indeed the eggs are swept up in this branding notwithstanding the fact that they will later emerge. However, if the eggs only formed after the chicken had already become treifah, then the argument to focus on the future outcome prevails and the eggs are spared from the chicken’s verdict of non-kosher (though, indeed, Chazon Ish explains, the eggs are prohibited as extensions of the chicken until they actually emerge).
Though we may not have solved the “chicken before the egg” dilemma here, you now know for sure that with regard to treifah, the treifah chicken must come before the eggs in order for them to be kosher.
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