הנוטל צריך להגביה ידיו (דהיינו ראשי אצבעותיו) למעל' שלא יצאו מים חוץ לפרק ויחזרו ויטמאו את הידים הגה וה"ה אם משפילן מתחלת הנטילה עד סופה דשפיר דמי רק שיזהר שלא יגביה תחלה ראשי אצבעותיו ואח"כ ישפילם דאז יצאו המים חוץ לפרק ויחזרו ויטמאו הידים (ב"י בשם מהר"י בן חביב) והיינו כשאינו נוטל כל היד עד מקום חבור היד עם הזרוע אבל אם נוטל עד שם א"צ להגביה ידיו (ויש חולקים בזה) וכן אם שפך על שתי ידיו רביעית בפעם אחת כיון דאין שם מים טמאים כלל א"צ להגביה ידיו וכן המטביל ידיו א"צ להגביה ידיו (וי"א דאם שופך על ידיו ג"פ אין צריך ליזהר בכל זה וכן נהגו להקל: (אגור בשם א"ז והגהות אשירי פכ"ה):

One who washes their hands must raise them (meaning the fingertips) upward so that the water does not flow past the wrist joint and return to defile the hands. Gloss: The same applies if one lowers them from the start of washing to the end — that is also valid — but one must be careful not to first raise the fingertips and then lower them, because then the water would flow past the wrist and return to defile the hands (Beit Yosef in the name of Maharai ibn Haviv). This applies when one does not wash the entire hand up to where the hand meets the forearm, but if one washes up to that point, there is no need to raise the hands (and some disagree). Similarly, if one poured a revi'it (a specific measure) over both hands at once, since there are no impure waters at all, there is no need to raise the hands. Similarly, one who immerses their hands need not raise them. (Some say that if one pours three times there is no need to be careful about all this, and this is the lenient custom) (Agur in the name of Or Zarua and Hagahot Asheiri, ch. 25.)

One who washes their hands pours a little of the revi'it to remove dirt and anything that interposes, then pours a second time (these waters are also impure), then pours a third time to purify the waters on the hands. If there is no dirt or interposing substance, one pours a full revi'it over both hands at once and does not need a second pouring. Gloss: Similarly, if one has abundant water, one first rinses a little to remove dirt, then pours a revi'it all at once and does not need a third pouring. One who washes their hands must rub them together. [Maimonides, Laws of Mikvaot ch. 11; Kol Bo; Semag; Rosh, ch. Kol HaBasar]

If one washed part of their hand and then added water to wash the rest with the same water, the hand remains impure as before, since there is no partial handwashing. However, if the part washed first still has enough moisture to moisten another surface (tofach al menat lehatfiach), it is pure. This applies to the first waters; for the second waters, one may wash part of the hand and add more water to the rest.

If one poured water on one hand and rubbed it against the other, the washing is invalid — even if afterward one poured water over both hands — because the water poured on one hand became impure, and when rubbed against the other hand, it defiled it. The second waters only purify water made impure by the hand itself, not water that came from the other hand. Therefore, one who poured from a vessel onto one hand and rubbed it against the other must dry their hands and wash again properly. Thus, it is preferable that someone else pour water for you; if there is no one, hold the vessel with your fingertips and pour over both hands at once, or pour a revi'it over each hand separately before rubbing — because pouring a revi'it at once is like immersion and does not require a second washing. If someone who has not washed their hands touches your hands while they are still wet, you must dry them and wash again, because they have been defiled through the water on them. Therefore, when pouring the third water (which serves as the "second" beyond the first), take care that one hand does not touch the other until the water has been poured on the second hand as well, or pour over both simultaneously. If one used a full revi'it for each hand, none of this is necessary.

From what has been written, it is clear that the defilement of one hand by rubbing against the other applies only when one washes one hand first and then rubs it against the other. But if one intends from the start to wash both hands together, both are considered as one hand and do not defile each other. Even four or five people who place their hands side by side or one atop the other are considered as one hand and do not defile each other.

If one washed each hand separately and then changed their mind, when receiving the second waters they joined their hands and poured over both at once, the hands are impure. When the hands were joined to receive the second waters, they defiled each other, since the water on one hand defiles the water on the other and the hand itself. When the second hand was washed, it did not purify the first waters (since they were defiled by the other hand); on the contrary, the second waters were also defiled. One must dry the hands and wash both together. Gloss: All the more so, one must be careful not to let a hand that received water once touch the hand that received water twice. [Mordechai, ch. Elu Devarim]

When rubbing the hands together, one must take care not to touch beyond the area where the water fell, because the hands defile each other in those areas.

If one washed one hand and rubbed it on their head (to dry it — which is why the hand does not become defiled, unlike the case in §164:2 where one scratched their head) or on a wall, and then touched the water that had come from the hand onto the head or wall — that hand becomes impure, because those impure waters returned and defiled it. Even though rubbing would have purified them before that, once one touched them again it is worse. It has already been explained that one who pours a revi'it at once is exempt from all this and there are no impure waters at all.

When pouring the first waters over the hands, one must take care not to leave a pebble, splinter, or any other object on the hand, since the water only purifies the water directly on the hand, not water resting on the object. But if one pours a full revi'it at once, there is no need for this caution.

One who has a wound on their hand with a bandage (ungüento in the vernacular) it is sufficient to wash the rest of the hand that is not covered by the bandage, and one must take care not to touch the bandage, lest the water on it return and defile the hand. Alternatively, one may pour a full revi'it over the hand at once, in which case the waters are not impure. [One pours the first waters whether over a vessel or over the ground. — Tur]