In this week’s parshah the Torah commands us in the prohibition of chaddash, not eating the new grain harvested before the korban Omer is brought on the second day of Pesach. The pasuk states “V’lechem v’kali v’karmel lo sochlu ad etzem hayom hazeh ad haviachem es korban elokaichem – And you shall not eat bread, etc. on this very day until you bring the offering of your God” (Vayikra 23:14). This pasuk teaches us that all of the five grains (wheat, spelt, rye, oats, and barley) from the time they are harvested are forbidden until after the korban Omer is brought.
As we do not have a Beis HaMikdash today and thus cannot bring the korban Omer, the new grain is permitted after the day the korban would have been brought. In Eretz Yisrael, that would be after the 16th day of Nissan; in chutz la’aretz, it is permitted after the 17th day of Nissan.
The Mishnah in Kiddushin 37b says that all mitzvos that are dependent on the land apply only in Eretz Yisrael except for urla (fruits that grow in the first three years of the trees life), and kilayim (not mixing different species), which apply even in chutz la’aretz. Rabbi Eliezer says that the prohibition not to eat chaddash applies in chutz la’Aretz as well. The Gemara there says that Rabbi Akiva agrees with Rabbi Eliezer and the halacha follows their opinion, and chaddash is prohibited even in chutz la’aretz.
The Mishnah and the Gemara do not discuss whether grain belonging to a non-Jew falls under this prohibition. Tosafos in Kiddushin, ibid, deduces from a Yerushalmi that grain of a non-Jew is in deed prohibited. The Rosh there prohibits grain grown by non-Jews as well.
The Bach (Yoreh Deah 293) came up with a revolutionary ruling in this matter, permitting grain that grew belonging to a non-Jew. This was one of the main hetterim used to permit drinking beer in Europe, at a time of need, when there was not much else to drink.
The Bach writes that he mentioned his insights to many of the leading gedolim and no one disproved him. Aside from disagreeing with Tosafos’s understanding of the Yerushalmi, and stating that he believes that the Rosh retracted his opinion in his teshuvos, the Bach brought his main proof from a Gemara in Rosh Hashanah (13a). The Gemara there asks: When Bnei Yisrael entered Eretz Yisrael, how did they bring a korban Omer? The Gemara says that they could not have brought the korban from grain that grew belonging to a non-Jew, for a korban Omer must be brought specifically from grain that grew belonging to a Jew. The Gemara then asks that perhaps they did not bring a korban Omer. The Gemara says that we know with certainty that they did bring the korban. This is because the pasuk says that on the day after the first day of Pesach the Bnei Yisrael ate from the good of the land. The Gemara deduces if they only ate on the second day of Pesach, then they must have not eaten from the land on the day before. What could have prevented them from eating and then permitted eating from the land? It must be that they brought a korban Omer, which permitted the prohibited grains.
The Bach asks, why did the Gemara have to deduce from the pasuk that they must have not eaten the day before. The Gemara could have brought a proof from the actual pasuk without deducing anything. If grain grown by non-Jews is prohibited, then all the grain around them was prohibited. If the pasuk says that they ate grain after the first day of Pesach, then they must have brought a korban Omer, since otherwise they could not have eaten anything.
From the fact that the Gemara had to prove that they did not eat on the day before by deducing it from the pasuk shows that it was not obvious that they could not eat before. And that is because grain grown by non-Jews is permitted. Therefore the majority of grain available was in fact permitted. It is for this reason that the Gemara could not simply prove from the fact that the pasuk says “they ate” that they brought a korban Omer because perhaps they ate the grain of the non-Jews.
The Shach and the Taz (the Bach’s son-in-law) disagree with the Bach. They maintain that grain grown by non-Jews is in fact prohibited, and they refute this proof by stating that perhaps there was old grain that the non-Jews had in their houses from previous years, which would be permitted. Thus, the Gemara could not simply cite the pasuk that says “they ate grain” to prove that they brought a korban Omer, because perhaps they ate the old grain from previous years.
The Shach and Taz both assume that the old grain from previous years from before the Bnei Yisrael entered Eretz Yisrael was permitted. It is unclear what the source for this is. One could argue that since the issur of chaddash did not take affect until Bnei Yisrael entered Eretz Yisrael, the old grain would be prohibited as well until the korban Omer was brought. In fact Tosafos in Rosh Hashanah, ibid d”h de’ikreivu, says that such grain would in fact be prohibited.