Chullin 126

We know from Leviticus 11:29–31 that the carcasses of a creeping animal (sheretz) — mice, lizards, etc. — transmit ritual impurity. But what about their eggs? According to the mishnah, intact eggs aren’t a problem, but perforated eggs are if someone comes into contact with them, regardless of the size of the hole. The reason is that while the shell does not convey impurity, the embryo does — at least at some stages of development. The Gemara comments:

One might have thought that even an egg in which tissue of an embryo has not developed imparts impurity. Therefore, the verse states: “that creep,” indicating that just as a creeping animal has developed tissue, so too only the egg of a creeping animal in which tissue of an embryo has developed imparts impurity.

Based on a close reading of Leviticus 11:29, the rabbis understand the embryo in the egg does not convey impurity unless it has developed actual flesh like a mature creeping animal. Therefore, an egg that contains an undeveloped embryo doesn’t meet the standard and can’t impart impurity, even if cracked. 

And even if the embryo has reached a level of development that it can creep, an intact egg does not convey impurity, as the Gemara next explains:

One might have thought that in the case of an egg in which tissue of an embryo has developed, it imparts impurity even if it was not perforated. Therefore, the verse states: “Whoever touches them when they are dead shall be impure,” indicating that when it is possible to touch the flesh, contact renders one impure; but when it is impossible to touch the flesh, one remains pure.

Again, the rule is based on a literal reading of Leviticus which requires physical contact for the contraction of impurity from a dead sheretz. Because you can’t touch a creeping animal’s embryo when the egg’s shell is intact, an undamaged egg poses no problem. The Mishneh Torah notes that this applies to an intact egg even when the embryo is visible inside.

The rabbis frequently delineate minimum quantities of a material needed to transmit impurity, and indeed, the Talmud also states:

How large must its perforation be to render one touching the egg or thigh bone impure? Its width must be the size of a strand of hair, as it is possible for one to touch the inside of an egg or thigh bone with a strand of his hair.

This answer makes it sound like any imperfection in the egg — even the proverbial hairline crack — renders it capable of conveying impurity. But there is a discussion in the later literature about what kind of hair we’re talking about (Rashi has especially strong feelings and insists that it’s either beard whiskers or hair on one’s head). Regardless of the specifics, we can appreciate that we’re talking about a very, very small crack being sufficient to allow contamination.

So we now have another piece of the extremely complex impurity puzzle: A creeping animal (sheretz), when dead or in embryo form, is impure to the touch. Intact eggs do not convey impurity, but damaged eggs with developed embryos do — even when the crack is miniscule. Even though these purity laws are not currently active, I wouldn’t recommend taking up a career in lizard egg juggling.

Read all of Chullin 126 on Sefaria.

This piece originally appeared in a My Jewish Learning Daf Yomi email newsletter sent on September 3, 2026. If you are interested in receiving the newsletter, sign up here.