One of the 39 acts of labor forbidden on the Sabbath is taking an item out of the private domain into the public domain. In the Mishnah an example, common in their era, was given of this forbidden act: A man is in the private domain, in his own home, and a poor person stands outside his home, in the public domain, asking for a hand-out. The person in the home hands the poor man a piece of bread. This man has transgressed the prohibition on taking items out of the private domain into the public; he took a piece of bread out of his home and put it in the hand of the poor person, in the public domain. The scholars asked: It is an accepted rule that in order to find someone liable for transgressing the prohibition on taking an item out of a private domain (the home) and into the public he must put the item, the bread, on a surface larger than 40 cm x 40 cm. Thus, for example, if the bread was placed on a pin or a thin pillar, the person who takes it from there does not transgress the prohibition. So, too, is the rule for one who places the item on a pin or a thin pillar whose area is less than 40 cm x 40 cm. If so, the poor man’s hand, outside the home, has an area less than required, so why did the early sages rule that he is transgressing the prohibition? Answer: The example brought in the Mishnah is according to the approach of Rabbi Akiva, who thinks that one does not require an area of 40 cm x 40 cm to be liable. The scholars asked: Though according to Rabbi Akiva one does not need the put the item on as large a surface as above, this is no proof that one need not remove the item from a surface of that size. A different sage, Rav Joseph, said that according to R’ Judah the Nasi there is no need to either remove or place the item on that large a surface to be liable for transgressing the prohibition on taking it out. The scholars rejected this answer, arguing that there is no clear source that Rabbi Judah the Nasi did not require a surface of 40 cm to hold one liable for taking the object out. Another sage, Rav Zira, argued that according to Rabbi Meir there is no need to rest the item on a large surface, and this, too, as rejected by the argument that there is insufficient proof that R’ Meir did not require a large surface to hold one liable for carrying.

Another sage, R’ Abba, argued that the example brought in the Mishnah deals with a poor person standing outside with a basket whose area is large, and that the bread was placed inside. A scholar, R’ Avihu, asked: Does not the Mishnah specify placing it “in his hand” and make no mention of placing it in a basket? This scholar argued that the example brought in the Mishnah deals with the manner in which the poor person sits, with his hand close to the ground; according to Halacha an air space of less than 30 cm is considered as though it did not exist and so it is as though his hand is on the ground, so it must be considered as though the bread were placed on the ground. The scholars asked: Does not the Mishnah speak of a poor man “standing,” meaning that he is not sitting? Answer: He stood, but he bent and placed his hand near the ground. Another possibility is that he stood within a depression and his hand was stretched out along the ground. Another possibility is that the poor man was a midget whose height was only 30 cm, so when he stood and stretched out his hand, the air space between it and the ground was under 30 cm and so it is considered as though his hand were on the ground. A scholar, Rava, asked whether it was the habit of the authors of the Mishnah to bring odd and unusual examples. This sage claimed, instead, that a hand, though its area is not 40 sq cm, is considered an important place to rest things and so one is liable for carrying items from the public to the private domain.
(Babylonian Talmud, Tractate Shabbat 4a-5a)