On which fire did Aharon place the Ketores?
When did he place the Ketores on the coals in the pan?
Torah Temimah (citing Yoma, 53a): When he is already in the Kodesh Kodshim. 1
As is implied by "Lifnei Hashem" - to counter the Tzedukim, who would place it there before entering the Kodesh Kodshim - See Torah Temimah note 52 - and who died on the spot.
Why does the Torah insert the (otherwise superfluous) phrase "Ve'chisah Anan ha'Ketores es ha'Kapores"?
Yoma, 53a: To teach us that adding 'Ma'aleh Ashan to the Ketores 1 is crucial to the Mitzvah.
In Pasuk #2 the Torah wrote "el-P'nei ha'Kapores asher al ha'Aron"; Why here, does it write asher al ha'Eidus"?
Oznayim la'Torah: To emphasize that the main objective of the Kapores was to cover, not the Aron, but the Luchos (ha'Eidus). Indeed, without the Luchos, the Aron itself served no purpose. 1
Oznayim la'Torah: Which explains why, in the tme of the second Beis-Hamikdash, when there were no Luchos, they did not make a new Aron to replace the old one.
Which Chiyuv Misah is the Pasuk referring to?
Rashi: For omitting any of the prescribed spices from the Ketores. 1
Sifra: For not adding the herb Ma'aleh Ashan
See Sifsei Chachamim.
Why must the cloud of smoke cover the Kapores?
Rosh (Shemos 30:1, citing the Ramban): "V'Chisah" is an expression of pardon - "Kisisa Chol Chatasam" (Tehilim 85:3). After the cloud covers the Kapores, he is assured "v'Lo Yamus."
