פירוש על זבחים 6:6

הבדיל בחטאת – that he pinched the bird’s neck with his finger nail two organs with the sin-offering.

Introduction Our mishnah teaches that if the priest deviates from some of the above instructions regarding the bird sacrifices, the sacrifice might still be valid. But if he deviates from others, they invalidate the sacrifice.

או לא הבדיל בעולה – that he pinched with it one organ.

If he did not remove the crop or the feathers or the entrails which came out of it, or did not dry it with salt, or made any other deviation after he had drained the blood out, it is still valid. The general rule here is quite clear if he makes any changes from the prescribed way of acting after he has drained out the blood, then the sacrifice is still valid.

פסול – for every kind of difference prior to the [Divine] service with the blood is invalid.

If he severed the [head of the] hatat or did not sever the olah, it is unfit. However, if he makes some changes before the blood is drained, such as severing the head of the hatar, or not severing the head of the olah, the sacrifice is invalid. It seems that the sacrifice is validated by the blood being drained out, and therefore deviations that occur before that moment can invalidate the sacrifice whereas those that occur after cannot.

ולא מיצה דם הגוף פסולה – for the essence of the blood is in the body, where it is found.

If he drained out the blood of the head, but not the blood of the body, it is unfit; The blood of the body, but not the blood of the head, it is fit. As far as the blood is concerned, the rule is that he must drain the blood out of the body, for that is where most of the blood is. If he does not do so, the sacrifice is invalid. He should also drain the blood out of the head, but if he does not, the sacrifice is still valid.