Gemara

90b (Beraisa): "Nishba Hash-m...Im Eshkach la'Netzach... Na'avor ha'Chodesh v'Nashbirah Shever" refers to people who hoard Peros.

"Veha'Shabas v'Niftecha Bar", "Lehaktin Eifah" and "u'Lehagdil Shekel" refer, respectively, to people who buy Peros to sell them in Shemitah, when they will be expensive, who give a smaller quantity of Peros, and lend on Ribis.

(R. Yochanan): An example of one who hoards Peros is Shabtai the hoarder. (He bought in order to sell to poor people at the high market price later in the year. One may hoard in order to sell to Aniyim at the low price when the market price will be higher.)

Shmuel's father would sell at the early (low) price (when grain is finished in the granaries).

Shmuel would not sell his own Peros until later when the market price was higher, but he sold at the early (low) price.

Chachamim of Eretz Yisrael: Your father was better than you!

This is because he deflated the early price, and ensured that prices will be low the entire year.

(Rav): One may delay selling his own Peros until the price rises.

Support (Beraisa): One may not hoard life-essential Peros (to sell later at a higher price), such as wine, oil and flour. One may do so with spices, such as peppers.

It is forbidden only to buy and hoard, but one may hoard what he grows himself.

One may buy and hoard in Eretz Yisrael (starting in the year before Shemitah) in order to sell in Shemitah and the following year (so there will be enough food in those years). In famine years, one may not hoard even one Kav of carobs, lest this increase prices.

R. Yosi b'Rebbi Chanina (to his servant): Buy and hoard for me starting in the year before Shemitah, in order to sell in Shemitah and the following year.

(Beraisa): We may not export life-essential Peros of Eretz Yisrael such as wine, oil and flour;

R. Yehudah ben Beseira permits exporting wine. This reduces (drunkenness and) immorality.

Just like we may not export to Chutz la'Aretz, we may not export to Surya;

Rebbi permits exporting from a town of Eretz Yisrael to a nearby town of Surya.

(Beraisa): We may not deal (buy in order to resell at a profit) in life-essential Peros of Eretz Yisrael such as wine, oil and flour;

R. Elazar ben Azaryah used to deal in wine and oil.

Regarding wine, he holds like R. Yehudah ben Beseira. Oil was plentiful in his area (so it was permitted to deal in it).

Rishonim

Rambam (Hilchos Mechirah 14:4): One may not do business in Eretz Yisrael with life-essential Peros. Rather, everyone brings from his granary and sells, in order that they will sell cheaply. Where oil is plentiful, one may profit on it.

Rambam (5): One may not store up life-essential Peros in Eretz Yisrael, or in any place that is mostly Yisre'elim, for this causes pain to Yisre'elim. This refers to one who buys in the market. One may store what he himself grows.

Magid Mishneh: Obviously, it is forbidden in a place that is mostly Yisre'elim. We may learn from the Heter to hoard (only what he grows himself), which is even in Chutz la'Aretz.

Rambam (6): One may hoard Peros for three years: Erev Shemitah, Shemitah and the year after Shemitah.

Magid Mishneh: The Rashbam says that we permit in order to sell them, lest people die when there is no food.

Rambam (ibid): In famine years, one may not hoard even one Kav of carobs, for this increases prices. One who jacks up prices or hoards Peros in Eretz Yisrael or a place that is mostly Yisre'elim is like one who lends on Ribis.

Rambam (7): This refers to life-essential Peros. One may hoard spices such as saffron and peppers in Eretz Yisrael or export them from place to place, like other extracts.

Magid Mishneh: We permit saffron and peppers, even though they are more commonly used than other spices.

Rambam (8): One may not export life-essential Peros such as wine, oil and flour from Eretz Yisrael to Chutz la'Aretz or Surya, nor from the jurisdiction of one king to that of another king in Eretz Yisrael.

Rosh (5:29): The Rashbam says that the Isur to hoard Peros is only in a city that is mostly Yisre'elim.

Nimukei Yosef (Sof 45b): Even when one may hoard Peros, e.g. in the three years starting Erev Shemitah, one may not do so if it is a famine year, for it greatly iNefelates prices.

Nimukei Yosef (46a DH Surya): Chachamim forbid exporting to Surya, for they hold that what an individual (David ha'Melech) conquered does not get Kedushah of Eretz Yisrael.

Poskim

Shulchan Aruch (CM 231:23): One may not do business in Eretz Yisrael with life-essential Peros. Rather, everyone brings from his granary and sells, in order that they will sell cheaply. Where oil is plentiful, one may profit on it.

Shulchan Aruch (24): One may not hoard life- essential Peros in Eretz Yisrael, or in any place that is mostly Yisre'elim. This refers to one who buys in the market. One may hoard what he himself grows. In famine years, one may not hoard more than what he needs to feed his family (Rema - for one year).

SMA (42): They (the Rambam and Shulchan Aruch) did not forbid business with life essentials in places in Chutz la'Aretz where most are Yisre'elim. This implies that it is permitted everywhere in Chutz la'Aretz, since there is a limit of how much one may profit (a sixth). Also, they bring the Isur of a double profit with eggs, which implies that it is permitted with other matters.

Shulchan Aruch (25): One who jacks up prices or hoards Peros in Eretz Yisrael or a place that is mostly Yisre'elim is like one who lends on Ribis.

SMA (43): This means that he transgresses "you brother will live with you."

Shulchan Aruch (26): One may not export life- essential Peros such as wine, oil and flour from Eretz Yisrael to Chutz la'Aretz or Surya, nor from the jurisdiction of one king to that of another king in Eretz Yisrael.

Beis Yosef (DH u'Mah she'Chosav uvi'Shnas): A Beraisa teaches that in famine years, one may not hoard even one Kav of carobs, lest this increase prices. The Rashbam explains that one may not hoard his own Peros, but he may leave himself enough for a year.

SMA (44): The Rosh and Tur did not bring this law. They hold that it is forbidden only in Eretz Yisrael, to promote settlement of Eretz Yisrael. It does not apply in Chutz la'Aretz, even if a place that is mostly Yisre'elim. Alternatively, since nowadays it is not common to have a place that is mostly Yisre'elim, this is like a law that does not apply, so they did not bring it.

Gra (11 and Be'er ha'Golah 70): The last law is like Chachamim who argue with Rebbi. They discuss within Eretz Yisrael.

Afarkasta d'Anya (2 OC 103): Some say that we may export Esrogim because they are planted with this intent. I say that they are not life- essentials. The Rashbam says that even eggs are not life-essentials!