Having already mentioned "Par" in the previous Pasuk, why does the Torah say "Veheivi es ha'Par" and not 'Veheivi oso'?
Sifra: To teach the Kohen Gadol that, unlike a Yisrael, who has the choice to bring a Se'eirah, he must bring specifically a bull. 1
Oznayim la'Torah: To remind the Kohen Gadol of the magnitude of his sin. 2
See Sifra and Ha'Torah ve'ha'Mitzvah.
Refer to 4:7:2:2. Oznayim la'Torah: The same applies to the Par Ha'Eidah, where the Torah also writes "al Rosh ha'Par", since they caused the Tzibur to sin.