And on the Festival itself he would ask only how the incident occurred, meaning that he would investigate the cause of the blemish, as in that case where a certain man who was a priest brought a firstborn before Rava, close to nightfall on a Festival eve. Rava was sitting and washing the hair on his head. He raised his eyes and saw the firstborn’s blemish. He then said to the owner of the firstborn: Go now, and come back tomorrow.
כי אתא למחר, אמר: היכי הוה עובדא? אמר ליה: הוה שדיין שערי בהך גיסא דהוצא, והוה איהו באידך גיסא. בהדי דבעי למיכל, עייל רישיה ופרטיה הוצא לשפותיה. אמר ליה: דלמא את גרמת ליה? אמר ליה: לא.
When he came back on the following day, Rava said to him: How did the incident that caused the blemish occur? The owner said to Rava: Barley grains were scattered on one side of a fence of thorns, while the firstborn was standing on the other side. When it wanted to eat, it stuck its head through the fence and a thorn cut its lip. Rava said to the owner: Perhaps you caused the blemish by deliberately placing the barley on the other side of the fence? He said to him: No.
ומנא תימרא דגרמא אסור, דתניא: ״מום לא יהיה בו״, אין לי אלא שלא יהיה בו מום, מניין שלא יגרום לו על ידי דבר אחר, שלא יביא בצק או דבלה ויניח לו על גבי האזן כדי שיבא הכלב ויטלנו — תלמוד לומר: ״כל מום״. אמר ״מום״, ואמר ״כל מום״.
The Talmud comments: And from where do you say that causing a blemish to an offering is prohibited? As it is taught in a baraita: It is written with regard to offerings: “There must not be any blemish in it” (Leviticus 22:21). I have only an explicit prohibition that it may not have a blemish; from where is it derived that one may not cause a blemish to it by means of something else, e.g., that he does not bring dough or a dried fig and place it on its ear so that a dog will come and take it, thereby biting off part of the animal’s ear and leaving it blemished? Therefore the verse states “any blemish.” It says “blemish” and it says “any blemish”; the word “any” comes to teach that one may not cause a blemish.