Parah 12:4 - 12:5

המזה מחלון של רבים – that stands in the window in the public domain and sprinkles there on the impure that pass by, and he sprinkled on an impure person thinking that the waters that are in his hands are pure for sprinkling.

ונמצאו פסולים – if he entered with this sprinkling to the Sanctuary, the impure person is example from a sacrifice [on his entering into the Sanctuary while impure], for this is a doubtful/uncertainty with regard to ritual impurity in the public domain (i.e., by Torah law, if uncertainty arises concerning the ritual purity of a person or an object, and that person or object is in a public domain, they are ritually pure. If the situation arises in a private domain, they are considered ritually impure) and his doubtful purity is deemed to be pure. And Maimonides explained the reason, that this impure person is under compulsion/unavoidably prevented, for he did not have in mind to check if the waters were fit/suitable for sprinkling or not, since he was standing in the public domain and sprinkling on many people. But if he stands in the window of a single individual and sprinkles, the impure person would have to check on the waters if they are fit/suitable, or not, and since he did not check, it is an inadvertent error but not something unavoidably preventable, and if he entered into the Sanctuary with this sprinkling, he is liable for a sacrifice, for this is like a doubtful impurity in the private domain where this doubt is impure.

שאין כהן גדול חייב על ביאת המקדש – as it is written (Numbers 19:20): “[If anyone who has become impure fails to purify himself, [that person shall be cut off from the congregation, [for he has defiled the LORD’s sanctuary],” the waters of purification are equivalent to the congregation, that is to individuals, excluding the High Priest, whose sin is not equivalent to that of individuals.

מחליקין היו (they would slip [on water]) – meaning to say, that there were so much waters of purification there until people would slip upon them, and even so they would trample on them, because they would not defile, since their Mitzvah was done.

בכנפו – in the corner of his garment. Because the ax that required sprinkling is a primary form of ritual defilement , and when he holds its corner the corner [of the garment] becomes first-degree of ritual impurity, but the person who holds is not impure, for a person and vessels do not receive defilement other than from a primary source of ritual impurity, and even though there is on the ax water sufficient for sprinkling, the person who holds it is not ritually impure because of carrying the waters of lustration, since the Mitzvah had already been fulfilled.

כדי שיטבול ראשי גבעולין ויזה (in order that he may dip the tips of the buds and sprinkle) - outside from what the hyssop absorbs.

כאילו הן על האזוב של נחושת – which does not absorb [water]. For we see the waters that are absorbed in the hyssop as if they are discernable/in natural form to complete the measure of sprinkling so that those who carry them are impure. And that which is written (Numbers 19:21): “he who sprinkled the waters of lustration”/"ומזה מי הנדה" [shall wash his clothes and whoever touches the water of lustration shall be impure until evening],” for they (i.e., the Rabbis) expound from this to the person who carries according to the measure of sprinkling, that is as if there were discernable/in natural form that they had the measure of sprinkling. But the Halakha is not according to Rabbi Yehuda.