Behonot

As part of his purity process the metzorah has to have the blood of the asham and oil put on his thumb, big toe and on his ear.  There are two ways this process.  It is either part of the completion of the kapparah of the korban or it may just be a separate din necessary for the purification of the metzorah.   

This seems to be a debate between Rashi and the Rambam.  The Rambam (Michuser Kippurim 4:3) says that one who eats the leftovers of the oil before the oil was placed on the metzorah is like one who eats kodshim before the blood is sprinkled.  It seems clear from this Rambam that the נתינת בהונות is part of the attonement of the sprinkling of the blood.  The Rambam indicates in Beas Mikdash 9:3 that a non-kohan is obligated even for placing the dam and the oil on the behonot of the metzorah (see Har Homorea.)  That makes sense only assuming the avodah of the behonot is part of the korban. 

Rashi on Yoma 24b says that a non-kohan is obligated only for the sprinkling of the blood, indicating there is no obligation for the placement on the behonot.  He follows this view in Zevachim 64a that the prohibition to eat the leftover oil before placing the behonot is only Rabbinic (based upon Masseh Yad.)

[It is also clear from Tosfos Yevamot 7a ד"ה לפי and Kiddushin 55b ד"ה ודילמא that the placing on the behonot is considered to be part of the avodah of the korban as pointed out by the Minchas Avrohom Yoma 61a, ואכמ"ל.  See also Mikdash Dovid 12:6.]