1)
Why does the Torah insert the (otherwise superfuous) words "Al ha'Nefesh ha'Shogeges be'Chet'ah bi'Shegagah"?
1.
Horayos, 7b: To teach us that a Kohen Gadol ("ha'Nefesh") is only Chayav to bring a Se'irah if he sinned 'be'He'elam Davar (following an erroneous ruling). 1
2.
Menachos, 74a: The fact that this follows the words "Vechiper ha'Kohen" implies that, in the event that the Kohen is the one who sinned, he is permitted to atone for himself. 2
