We learned there [Mishnayos Maasros]: One who is peeling barley [an unusual way of processing] can peel off one grain at a time and eat it [it is considered ‘casual eating’ which is not obligated in Terumos and Maasros], but if he peels to put in his hand [more than one at a time, it is considered processing and] he is obligated in Terumos and Maasros.
Rabbi Elazar: The same applies to Shabbos [threshing is a Melacha, but if he peels only one at a time, it is not considered a Melacha].
Challenge: It’s not so [it cannot be that peeling more than one grain of barley is considered a Melacha on Shabbos]! “Rav’s wife would peel cupsful for him on Shabbos”, and “Rav Chiya’s wife would peel cupsful for him on Shabbos”.
Resolution: If we are to accept Rabbi Elazar’s interjection in the Mishnah, it must be referring to the second part of the Mishnah: One who rubs grain may blow it (058) from his hand, a bit at a time, and he may eat [without separating Maaser]. But if he blows and places it in his lap, it is obligated in Maaser.
Rabbi Elazar: The same applies to Shabbos.
Rabbi Abba bar Mammal: So are you saying that the first part of the Mishnah applies only to Maaser and not to Shabbos? Is there such a thing that is considered a Melacha [processed] with regard to Maaser, but not with regard to Shabbos?
Rav Sheishes brei d’Rav Idi: Isn’t there such a distinction with regard to the “Goren of Maaser”?
Mishnah: What is the Goren [the finished pile] of Maaser [for the following vegetables]? Cucumbers and pumpkins, when the flower falls off. If the flower doesn’t fall off, it is considered ready when he piles them into a heap.
The same is learned regarding onions: “when he piles them into a heap”.
But with regard to Shabbos, collecting vegetables into a pile is not considered a Melacha. How would you explain this? That with regard to Shabbos only a Melacha requiring skill is considered a Melacha, so you can apply the same explanation to the distinction between peeling barley and rubbing grain.
Question: How may one rub grain on Yom Tov?
Abayye in the name of Rav Yosef: One finger on top of one finger.
Rav Avya in the name of Rav Yosef: One finger over two fingers.
Rava: As long as he’s making a shinui [not rubbing it with both hands], it is permitted even to do it over all fingers [as long as it’s being done with one hand.