Siman 600

Know that the two days of Yom Tov of Rosh Hashanah are not similar to the two days of Yom Tov of the other festivals, for regarding the other festivals they observe only one day in Eretz Yisrael, but Rosh Hashanah they observe even in Eretz Yisrael for two days even today, as the Rif wrote in the first chapter of Beitzah. And the reason for the matter is: that at the time when they would sanctify based on the sighting, all the festivals were clear in Eretz Yisrael as to which day they fell, since many days had passed from Rosh Chodesh. And only in the diaspora, a place where the messengers of the beit din do not reach, they would observe two days because of the doubt, for they did not know on which day Rosh Chodesh was established. And therefore, even though now we are expert in the fixing of the month, as we establish the months based on the calculation from the days of Hillel the Prince and onward – nevertheless, the original enactment stands in its place. However, in any event, one of them is certainly chol, and its initial practice was only because of the doubt.

But on Rosh Hashanah, which is on Rosh Chodesh itself—even in Jerusalem they would many times observe two days. That is: if the witnesses of the sighting came on the first day, having seen the birth of the moon—they would observe only the first day. But if they came at night after the first day, and certainly if on the next day—then Rosh Chodesh and Rosh Hashanah were established for the next day, and on the first day they also practiced holiness in their anticipation that witnesses would come. And even if witnesses came on the first day from the time of mincha and onward—they also practiced observing two days of Rosh Hashanah, as we learned in a Mishnah in the fourth chapter of Rosh Hashanah. Thus it is found that in most years they observed two days of Rosh Hashanah even in Jerusalem. And this was not due to doubt, but rather because such was the enactment. Therefore, we observe two days until today. And this is what our sages, of blessed memory, said, that it is like a "long day," meaning that both of them are certainly holy, and one is not mundane as with another Yom Tov. (And there is a sugya and matter regarding this in Beitzah 5b for Rashi, and Tosafot, and the Rif, and the Rosh. However, for the law, so it is.)

Therefore, on Rosh Hashanah several laws of muktzeh and nolad change on Rosh Hashanah from other festivals. For on every festival—an egg that was laid on this one is permitted on that one. And similarly, milk that was milked on the first day is permitted on the second. But on Rosh Hashanah it is not so, because on all festivals—one of them is mundane, but on Rosh Hashanah both of them are holy, and it is like a long day. Only regarding a corpse did they leniate on the second day of Rosh Hashanah, due to the honor of the deceased as I wrote in siman 526, and not in other matters. And similarly, a thing that was trapped or a thing that was detached on the first festival day of Rosh Hashanah is forbidden on the second, as I wrote in siman 515, see there.

And based on this, a dispute arose among the Rishonim whether to say "shehecheyanu" in the kiddush and for the shofar on the second day of Rosh Hashanah. And the Tur brought a responsum from Rashi, of blessed memory, who wrote: My teachers say that one should not say the blessing of time on the second day, for it is as one day. But I say that one must say the blessing of time, for it is like a long day regarding other matters; however, the essence of the Yom Tov from the Torah is only one day. And most of the poskim agreed with Rashi. Yet in order to fulfill the opinion of the Geonim, the common custom in all lands is to take a new fruit at the time of kiddush, for in any case one must say "shehecheyanu"; or to wear a new garment. And for the shofar, where a fruit is not relevant—he should wear a new garment. And all this is not a requirement, for the common custom is to make "shehecheyanu" in all manners. And even though in kiddush we place a new fruit, behold, during the blasts the blower does not wear a new garment and bless "shehecheyanu." And so too in kiddush, if he does not have a new fruit—nevertheless he blesses "shehecheyanu." And so wrote our teacher, the Rema. (And the Beit Yosef regarding kiddush ruled to bless "shehecheyanu," but not regarding the blasts, except when the first day falls on Shabbat. And it is a wonder: what is the difference between shofar and kiddush? See the Beit Yosef, and it requires further study.)