The Mishnah taught: If he is working with his hands but not his feet...

Beraisa: (When does the Torah allow him to eat? When he is working) with his hands or squashing with his feet, or even if he carries on his shoulder.

R. Yosi bei R. Yehudah: He must be using his hands, his feet and his body. This excludes if he only uses his hands but not his feet or his feet but not his body.

The Gemara explains: R. Yosi bei R. Yehudah says that we learn from the word "dayish'' - "threshing'' (in Devarim 25, 4 - "Do not muzzle an ox in its threshing'' - threshing) involves food that grows in the ground; this excludes one who milks, makes cheese or curdles, as they do not grow in the ground.

Threshing (also) involves produce whose processing is unfinished; this excludes wine when it is in the pit, having had its impurities removed. Since its production was completed, the worker cannot eat from it because it has become obligated in Maaser.

If one separates pressed dates or splits up pressed figs, their production was already completed when the fig/date cakes were made (and the worker cannot eat from them because they have already become obligated in Maaser).

Threshing (also) does not obligate produce in tithing; this excludes one who kneads, shapes and bakes dough, as through these actions, it is brought to an obligation to tithe.

(Mishnah): If he was working with figs, he may not eat grapes and vice-versa. However, he may delay eating until he reaches an area with better produce.

In all cases, workers should only eat at the time of the completion his work (that he may now sit down and eat the fruits). However, in order not to waste the time (and money) of the employer, the Chachamim permitted them to eat whilst walking from one row to the next and whilst returning from the winepress.

A donkey may eat while be unloaded.

(Gemara) - R. Ila: The pasuk states (Devarim 23, 25), "When you shall come to the vineyard of your friend you may eat grapes as you desire, until you are satiated''.

What else could one eat in a vineyard? Rather, the word "grapes'' is to teach you that if he works with grapes, he cannot eat figs (that are growing nearby).