Rif Rosh HaShana 2b {Rosh haShana 10a - 12b}

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2b

{Rosh haShana 10a}
and the fruits of this planting are forbidden until the 15th of Shevat, whether because of Orlah {of the first three years}, or because of Neta Revai {of the fourth year}.

From where do we know this? For it is written {Vayikra 19:23}:

כג וְכִי-תָבֹאוּ אֶל-הָאָרֶץ, וּנְטַעְתֶּם כָּל-עֵץ מַאֲכָל--וַעֲרַלְתֶּם עָרְלָתוֹ, אֶת-פִּרְיוֹ; שָׁלֹשׁ שָׁנִים, יִהְיֶה לָכֶם עֲרֵלִים--לֹא יֵאָכֵל.

23 And when ye shall come into the land, and shall have planted all manner of trees for food, then ye shall count the fruit thereof as forbidden; three years shall it be as forbidden unto you; it shall not be eaten.

כד וּבַשָּׁנָה, הָרְבִיעִת, יִהְיֶה, כָּל-פִּרְיוֹ--קֹדֶשׁ הִלּוּלִים, לַיהוָה.

24 And in the fourth year all the fruit thereof shall be holy, for giving praise unto the LORD.

כה וּבַשָּׁנָה הַחֲמִישִׁת, תֹּאכְלוּ אֶת-פִּרְיוֹ, לְהוֹסִיף לָכֶם, תְּבוּאָתוֹ: אֲנִי, יְהוָה אֱלֹהֵיכֶם.

25 But in the fifth year may ye eat of the fruit thereof, that it may yield unto you more richly the increase thereof: I am the LORD your God.

{and reading all the selected citations together, it seems that that prohibition extends to the fifth year.}
How so?
There are times that the fourth year is prohibited because of Orlah {thus extending the prohibition of verse 23 to verse 24} and there are times that the fifth year is prohibited because of Revai {thus extending the prohibition from verse 24 to verse 25}.
From here you deduce that they are prohibited until the 15th of Shevat.

{Rosh HaShana 10b}
And we establish this as like Rabbi Meir who said that a single day in the year is reckoned as a year, and when do we need 30 days? for taking root. And if so, it is logical that it would require 31 days, but Rabbi Meir maintains that the 30th day is counted here and there.

And another brayta teaches: One may not plant, slip, and graft erev Sheviit less than 30 days before Rosh HaShana, and if he planted, slipped, or grafted he should uproot. These are the words of Rabbi {alternate: Rabbi Eleazar}. Rabbi Yehuda says: any grafting which does not take root within 30 days will not take subsequently take root. Rabbi Yossi and Rabbi Shimon say: Two weeks.

Rav Nachman cited Rabba bar Avuah: According to the one who says 30 days, you need 30 days and 30 days. And according to the one who says 3, you need 3 and 30. And according to the one who says 2 weeks, you need 2 weeks and 30.

And we learn in perek heArel {Yevamot 83a}: They said in the academy of Rav in the name of Rav: The halacha is like Rabbi Yossi by an androgenos and by grafting.
And we say: what is this to me by grafting?
Shmuel said: Come and hear: For Rav {change from Shmuel} said to Rav Anan: Teach in accordance with the one who says 3 and 30.

And this matter is one of prohibition, and we establish that the halacha is like Rav in prohibitions.

They learnt {in a brayta}: Rabbi Eliezer says: In Tishri, the world was created. In Tishri, the forefathers were born. In Tishri, the forefathers died. On Pesach, Yitzchak was born. On Rosh HaShana, Sarah, Rachel, and Chana were visited {with child}. On Rosh HaShana, Yosef left the dungeon. On Rosh HaShana, the labor was nullified for our ancestors in Egypt. In Nissan, they were redeemed, and in Nissan, we will be redeemed in the future.

{Rosh HaShana 11a}
It was taught: On the 1st of Tishri is the Rosh haShana for herbs for tithes and for vows.
{Rosh haShana 12b}
For what practical halachic purpose {vows}?
For like that which we learnt {in a brayta}: One who vows off benefit from his friend for a year, we count 12 months from day to day. If he says "for this year," even if he is standing there on the 29th of Elul, once the 1st of Tishri arrives, he has his year.

And even according to the one who holds that one day to the year is not considered a year, here, to pain himself he accepted this upon himself, and he has been pained.
And say rather Nissan?
By vows, it goes