Zevachim 58A

מתני׳ קדשי קדשים ששחטן בראש המזבח ⁠– רבי יוסי אומר: כאילו נשחטו בצפון. רבי יוסי ברבי יהודה אומר: מחצי המזבח ולדרום ⁠– כדרום, מחצי המזבח ולצפון ⁠– כצפון.

Mishnah: It was taught in the previous chapter that offerings of the most sacred order are to be slaughtered in the northern section of the Temple courtyard. With regard to offerings of the most sacred order that one slaughtered atop the altar, R' Yosei says: Their status is as though they were slaughtered in the north, and the offerings are therefore valid. R' Yosei, son of R' Yehuda, says: The status of the area from the halfway point of the altar and to the south is like that of the south, and offerings of the most sacred order slaughtered in that area are therefore disqualified. The status of the area from the halfway point of the altar and to the north is like that of the north.

גמ׳ אמר רב אסי אמר רבי יוחנן: אומר היה ר׳ יוסי, כוליה מזבח בצפון קאי. ומאי ״כאילו״? מהו דתימא בעינן ״על ירך״⁠ – וליכא; קא משמע לן.

Talmud: Rav Asi says that R' Yoḥanan says: R' Yosei used to say: The entire altar stands in the north section of the Temple courtyard. The Talmud asks: And what is the meaning of R' Yosei’s statement that if one slaughtered offerings of the most sacred order atop the altar it is as though they were slaughtered in the north, which indicates that they were not actually slaughtered in the north? The Talmud answers: R' Yosei said this lest you say that we require that the offering be slaughtered “on the side of the altar northward” (Leviticus 1:11), i.e., on the ground beside the altar, and that requirement is not fulfilled when it is slaughtered on top of the altar. Therefore, R' Yosei teaches us that the offering is still valid.