Chullin 19
מפני שדרכן של שרצים לגלות ואין דרכן לכסות
Because it is the habit of reptiles to uncover [a vessel]<span class="x" onmousemove="('comment',' Therefore, in the second case the alternatives are (a) the bowl might have been uncovered by a reptile or by a clean person - in either case the water remains clean; (b) it might have been uncovered by an unclean person which would make the water unclean. The chances being more in favour of the first alternative, the water is regarded as clean on the principle of following the majority.');"><sup>1</sup></span>
(אי נמי טעמא דהניחה מגולה ובא ומצאה מכוסה מכוסה ובא ומצאה מגולה הא מצאה כמה שהניחה לא טומאה איכא ולא פסולה איכא)
but not to cover one.<span class="x" onmousemove="('comment',' Therefore, in the first case, as the possibility of a reptile having covered the bowl is excluded, the only alternatives are that it was covered either by a clean person or by an unclean person; and as the one is not more probable than the other, the law adopts the stricter view and regards the water as unclean.');"><sup>2</sup></span>
ש"מ
Whereas, in the case of water left uncovered, if there is any doubt about it, it is forbidden.<span class="x" onmousemove="('comment',' On the ground of danger to life. In cases regarding uncleanness however, it is clear from the foregoing statements that the law does not always adopt the stricter view; v. n. 2.');"><sup>4</sup></span>
כמה ישהו ויהיו אסורין
Three liquids are prohibited if left uncovered; water, wine and milk.<span class="x" onmousemove="('comment',' It is feared that these liquids might have been poisoned by a snake or by other poisonous reptiles.');"><sup>6</sup></span>
ישתה
And drink therefrom'! Then you see it!<span class="x" onmousemove="('comment',' According to the time limit here laid down, it is clear that a man who came at the end of this period would see the reptile at the vessel, if any reptile had come; and there would therefore be no doubt but that the liquids had been poisoned. If, on the other hand, no reptile is seen, it is clear that no reptile could have been there in his absence.');"><sup>7</sup></span>
אלא ישתה ויחזור לחורו:
It was stated: If a man slaughtered with a knife<span class="x" onmousemove="('comment',' It is assumed throughout the whole of this discussion that the knife was perfectly good at the beginning, i.e., it had been examined before the slaughtering and pronounced to be free from notches.');"><sup>8</sup></span>
איתמר
which was found afterwards to have a notch in it, R'Huna says, even if he broke bones with it the whole day long [after the slaughtering], the shechitah is invalid, because we apprehend that it became notched while cutting the skin [before actually cutting the throat].
ורב חסדא אמר
but what is the reason of R'Hisda's opinion? - He reasons thus: A bone certainly notches [the knife], whereas the skin may or may not notch [the knife]; there is thus a doubt against a certainty, and a doubt cannot set aside a certainty.
אמר לך
and then there was found something adhering to his body,<span class="x" onmousemove="('comment',' This substance may have been adhering to his body before the immersion and interposed between the water and his flesh, to which case the immersion is invalid.');"><sup>11</sup></span>
עצם ודאי פוגם עור ספק פוגם ספק לא פוגם הוי ספק וודאי ואין ספק מוציא מידי ודאי
even though he was using that particular substance all day long [after his immersion], it is not regarded as a proper immersion unless he can declare: 'I am certain it was not upon me before [my immersion]' - Now in this case, he certainly immersed himself, and there is a doubt whether the substance was or was not upon him [before his immersion], yet the doubt sets aside the certainty! - This case is different, for one can say: Let the unclean person remain in his [unclean] status, and assume that there has been no immersion.
והא הכא דודאי טבל ספק הוה עליה ספק לא הוה עליה וקאתי ספק ומוציא מידי ודאי
An objection was raised: If one cut through the gullet<span class="x" onmousemove="('comment',' The statement deals with the slaughtering of a bird, in which case it is sufficient to cut through one organ, either the windpipe or the gullet.');"><sup>12</sup></span>
ה"נ העמד בהמה על חזקתה ואימר לא נשחטה
If one cut through the gullet and then the windpipe was found to be torn away, and it is not known whether it was torn away before or after the slaughtering - this was an actual case [brought before the Rabbis], and they ruled: Any doubt whatsoever arising about the slaughtering makes it invalid.