Why does he take blood that was thrown on the Mizbe'ach?!
Chizkuni: It was in order to join (Shemen ha'Mishchah) to the Mizbe'ach. 1
Da'as Zekenim and Hadar Zekenim left this difficult. After Zerikah, its Mitzvah was done, and the Kedushah is gone, e.g. if it spilled on a garment, it need not be washed (Zevachim 93a) (PF).