Yoma 53A

שלא תתחיל מפניך, שמא תכוה.

not to begin piling the incense in front of you, i.e., from the side closest to you, lest you be burned. If the priest were to place the incense on the side directly in front of him and then proceed to spread it toward the Ark, his hands would pass over the incense that is already burning and he might burn himself.

תנו רבנן: ״ונתן את הקטורת על האש לפני ה׳״⁠ — שלא יתקן מבחוץ ויכניס. להוציא מלבן של צדוקין, שאומרים יתקן מבחוץ ויכניס.

§ A baraita states: “And he should put the incense upon the fire before YHWH” (Leviticus 16:13); this means that he should not prepare by placing the incense outside, in the Sanctuary, and bring into the Holy of Holies a coal pan holding the burning incense. This was emphasized in order to exclude the opinion of the Sadducees, who say that he should prepare the incense outside and then bring it in.

מאי דרוש? ״כי בענן אראה על הכפורת״⁠ — מלמד שיתקן מבחוץ ויכניס.

The Talmud asks: What did the Sadducees interpret; what verse do they cite as the basis for their opinion? The Talmud answers that it was the verse: “For I will appear in a cloud upon the Ark cover” (Leviticus 16:2), which the Sadducees say teaches that he should prepare it outside, so there would already be a cloud of incense, and only then should he bring it inside the Holy of Holies.

אמרו להם חכמים, והלא כבר נאמר: ״ונתן את הקטורת על האש לפני ה׳״. אם כן, מה תלמוד לומר: ״כי בענן אראה על הכפורת״⁠ —

The rabbis said to them: Wasn’t it already stated explicitly: “And he should put the incense upon the fire before YHWH” (Leviticus 16:13), which indicates that the High Priest should present the incense only when he stands before God in the Holy of Holies? If so, what is the meaning when the verse states: “For I will appear in a cloud upon the Ark cover” (Leviticus 16:2)? This verse does not mean that there should already be an incense cloud before he enters.