מדרש אויף ויקרא 4:31

5) "and the Cohein shall make atonement for him": (This teaches us that) the atonement must be expressly for him (the owner of the offering), that he not atone for two at one time (by mixing the blood of the two offerings), and that the Cohein (performing the service) may atone for himself (i.e., It is not necessary that another Cohein perform the service for him.) "and it shall be forgiven him": his sin is not left "suspended" until Yom Kippur, (but he is forgiven completely). I might think that even if he (the Cohein) "sat" and did not offer it (the owner nevertheless receives atonement); it is, therefore, written ("and it shall be forgiven) him" (i.e., only him for whom the service has been performed.)

5) (Vayikra 4:35): "And he shall atone for him," (Vayikra 4:31): "And he shall atone for him," (Vayikra 4:26): "And he shall atone for him." What is the intent of this? (i.e., Why three times?) It is needed. For it might be reasoned: Blood is mentioned (as being applied) below (the red line on the altar [i.e., the blood of burnt-offerings, etc.]), and blood is mentioned (as being applied) above the red line (i.e., the blood of sin-offerings, applied on the four horns). Just as with the blood applied below, one application atones, so, with the blood applied above, one application (on one horn) atones.

8) (Vayikra 4:26): "And the Cohein shall make atonement for him, and it shall be forgiven him."): "And he shall make atonement for him": (This teaches us that) the atonement must be expressly for him (the owner of the offering), that he not atone for two at one time (by mixing the blood of two offerings), and that the Cohein (performing the service) may atone for himself (i.e., It is not necessary that another Cohein perform the service for him.) "and it shall be forgiven him": his sin is not left "suspended" until Yom Kippur, (but he is forgiven completely). I might think that even if he (the Cohein) "sat" and did not offer it (the owner nevertheless receives atonement); it is, therefore, written ("and it shall be forgiven) him" (i.e., only him for whom the service has been performed.)