Commento su Yadayim 2:1

נטל את ידו משטיפה אחת – we call it one rinsing all the while that he didn’t pour other than on one hand until the joint/wrist, and it is sufficient once with his one hand, even though there isn’t in the vessel one-quarter of a LOG other than it comes from the remnants of purity. But for both of his hands, even though they come from the remnants of purity, they are not effective until he pours twice. The first [rinsing] until the joint/wrist and the second time up until the joint/wrist. But Maimonides explains: from one pouring is from one rinsing [of water on his hands]. But when he pours both of his hands with one rinsing, the waters become defiled on his one hand, and it is found hat he washes the second with water that became defiled, and his hands were not purified until he poured a second [rinsing] of water from one-quarter of a LOG. But when he pours [water] on only one hand, through that rinsing, his hand is purified, but when he pours water a second time to purify the water that is on his hand, it is sufficient with less than one-quarter of a LOG. But the Halakha is not according to Rabbi Meir.

If he poured water over one of his hands with a single rinsing his hand becomes clean. The person poured water over only one hand, because he intended to eat with only one hand. He also only poured one pouring, and not two. His hand is pure even if he didn't pour the full 1/4 log because the water comes from a vessel with a pure 1/4 log. However, if the water came from a vessel with a lesser amount, his hand would not be pure.

נפל ככר של תרומה – where he poured the first waters from one-quarter of a LOG [of a single rinsing] and a loaf of heave-offering/Terumah fell up upon them, or a loaf of heave-offering came in contact with the waters that were on his hand prior to his drying them, or prior to his pouring upon them a second time [for consuming heave-offering].

If over both his hands with a single rinsing: Rabbi Meir declares them to be unclean until he pours a minimum of a quarter of a log of water over them. If he tries to do this with both hands, meaning pour water over them only once, there must be at least 1/4 of a log poured over the two hands. Rabbi Meir holds that if one uses the full 1/4 log, he doesn't need to wash off the first water that he poured onto his hands. However, if he pours water twice over his hands, then his hands are pure even if he didn't pour a full 1/4 log as long as they came from a vessel with at least 1/4 of a log in it.

טהור – for just as they are effective to purify his hands, they are also effective to purify themselves.

If a loaf of terumah fell on the water the loaf is clean. Rabbi Yose declares it to be unclean. If a loaf of terumah falls on the water that he used to wash his hand, the first opinion holds that the loaf is still clean. According to this opinion the water is clean. Rabbi Yose holds that the water purified the hands, but it itself has become impure.

ר' יוסי מטמא – for he holds that they are effective to purify his hands, but they themselves are impure.