Yoma 44B

אלא בשעת הקטרה.

except during the burning of the incense.

והא איכא הא מעלה, דאילו מהיכל פרשי בין בקדושה דידיה, בין בקדושה דלפני ולפנים, ואילו מבין האולם ולמזבח לא פרשי אלא בקדושה דהיכל! אמר רבא: שם פרישה אחת היא.

But there is also this higher standard, that whereas from the Sanctuary they remove themselves both during its own sanctification, i.e., the blood presentations in the Sanctuary, and during the sanctification of the innermost chamber, i.e., the Holy of Holies, but from the area between the Entrance Hall and the altar, they remove themselves only during the sanctification of the Sanctuary. Rava said: Indeed, there are numerous distinctions, but the baraita teaches only one because all the distinctions fit into one category of removal.

אמר מר: כך פורשין בשעת מתן פר כהן משיח, ופר העלם דבר של צבור, ושעירי עבודה זרה. מנא לן? אמר רבי פדת: אתיא ״כפרה״ ״כפרה״ מיום הכפורים.

The Talmud continues to analyze the baraita: The Master said in the baraita: Just as they remove themselves from the area between the Entrance Hall and the altar during the burning of the incense, they similarly remove themselves during the blood presentations of the bull of the anointed priest; of the bull for an unwitting communal sin; and of the goats of idol worship. From where do we derive this? R' Pedat said: It is derived by a verbal analogy between the word atonement said in connection with those offerings and the word atonement from the prohibition on Yom Kippur.

אמר רב אחא בר אהבה, שמע מינה: מעלות דאורייתא, והכי גמירי להו.

Rav Aḥa bar Ahava said: Learn from this that there is a prohibition in the area between the Entrance Hall and the altar. The higher standards applied to the various areas in the Temple are defined by Torah law, and the rabbis learned them as a tradition.

דאי סלקא דעתך דרבנן, מאי שנא בין האולם ולמזבח? דילמא מיקרו ועיילי ⁠— מכולה עזרה נמי נפרשו, דילמא מיקרו ועיילי!

As if it could enter your mind that these standards are defined by rabbinic law, what is different about the area between the Entrance Hall and the altar that the prohibition applies only there? Perhaps other priests would accidentally happen to enter the Sanctuary while incense is burning there. But if that is the reason, then the rabbinic decree should require that they remove themselves also from the entire Temple courtyard, since perhaps they would accidentally happen to enter. The fact that the prohibition does not extend to the Temple courtyard suggests that the standards are defined by Torah law.