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R. Yanai says that Tevel is not Chayav in Ma'aser until it is brought into the house through the entrance and not by way of the roof or backyard.
R. Yochanan says even if the Tevel was brought into a guarded courtyard it is Chayav in Ma'aser
When a worker eats from the produce he may eat from it without separating Ma'aser.
If someone purchases produce prior to the Gmar Melachah for Ma'aser he may not eat from the produce without separating Ma'aser. (1)
If the bark of a fig tree is outside the courtyard and a branch was sticking into the courtyard or the house and the owner pulled off a fig in the house he may eat it without separating Ma'aser. (2)
Min ha'Torah if a person does the Gmar Melachah in order to sell it the produce it is Patur from Ma'aser and a person who purchases produce is also Patur from Ma'aser.
If one doesn't allow a worker to eat from the produce that he is working it is not a transgression of the prohibition of muzzling an animal while it is threshing.
The Gmar Melachah of cucumbers and pumpkins is when the blossom on the top starts falling off.
A worker may eat from the produce that he is working on whether it is not yet harvested or it is already harvested. (3)
It is forbidden to muzzle can ox while it is working whether it is working on unpicked produce or produce that has already been harvested.
A BIT MORE
1. Since it is not yet the Gmar Melachah for Ma'aser the Ba'al ha'Bayis may eat from the produce without separating Ma'aser, however if someone purchases the produce he is obligated to separate Ma'aser because a purchase has the same Din as A Gmar Melachah. A worker the same as a purchaser and he may eat without separating Ma'aser.
2. Even though the Ba'al ha'Bayis is eating the fig in his courtyard or his house it is Patur from Ma'aser since the bark of the tree is more important to him than the branch and therefore the Ikar is the bark and until he harvests all of the fruit of the tree and brings them into the house it is Patur from Ma'aser, however if someone purchases the fruit it is Chayav in Ma'aser because the fruit that he purchased is important to the purchaser not the bark of the tree and since the fruit was in the house it is Chayav in Ma'aser.
3. If it is not yet harvested he may eat from it if it is the Gmar Melachah and if it is harvested he may eat from it if it is not yet the Gmar Melachah for Ma'aser.
A MUZZLED WORKER
If one doesn't allow a worker to eat from the produce that he is working on it is not a transgression of the prohibition of muzzling an animal while it is threshing. Rashi states that this applies whether you forcibly stopped the worker from eating or he conditioned the work on the worker not being allowed to eat. The Ritva states that if he forcibly stopped the worker from eating he must pay the worker the value of the produce that he otherwise would have eaten.
A person is not obligated to separate Ma'aser Min ha'Torah unless he does the Gmar Melachah in order to eat the produce, but if he does the Gmar Melachah in order to sell the produce it is Patur Min ha'Torah but it is Chayav d'Rabanan. Also, someone who purchases produce is Patur Min ha'Torah from separating Ma'aser but he is Chayav d'Rabanan. However, he is only Patur from separating Ma'aser if the Gmar Melachah was done by the seller, but if the Gmar Melachah was done by the buyer it is Chayav in Ma'aser. (Rambam Hilchos Ma'aser 2:1, 2)
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