Zevachim 6:5-6

Zevachim 6:5

Burnt offerings of birds were prepared as follows: the kohein went up the ramp, turned to the walkway, and came to the southeast corner of the altar. There, he nipped the head of the bird at the nape, severing it. He drained the blood on the wall of the altar, then took the head and held the place where it was nipped against the wall of the altar. He rubbed salt on it and threw it on the fire. He then took the body, removed the crop, the feathers, and the innards that come out with the crop, and threw them on the altar ashes. He slit the bird open but he did not sever it; if he severed it, the sacrifice remains valid. He rubbed salt on this as well and threw it on the fire.

Zevachim 6:6

If he didn’t remove the crop, the feathers, or the innards that come out with the crop, if he didn’t rub salt on it, or if he did anything differently after draining the blood, the sacrifice remains valid. If he severed the head of a sin offering from the body, or if he didn’t sever the head of a burnt offering, he has invalidated the sacrifice. If he drained the blood from the head but not from the body, the sacrifice is invalid; if he drained the body but not the head, it remains valid.