A chiddush similar to that of R’ Zalman Baron can already be found in the Shu”t Binyan Shlomah (1:48). The Binyan Shlomah is mechadesh [offers a novel ruling], that although during the final days of Succos (all days except the first one) one can fulfil the mitzvah of arbah minim with a borrowed set, and in a year when the first day of Succos falls on Shabbos and we don’t take the arbah minim it would seem that having a borrowed set the entire Succos would be perfectly ok, one should still be careful and make sure to pay for it before Succos. We must anticipate the arrival of Moshiach and the rebuilding of the Beis HaMikdosh, and that there will be a mitzvah of daled minim even on Shabbos, and in such a case a borrowed set will be pasul. Therefore, to be on the safe side, one should make sure his arbah minim are 100% his by the time Succos arrives.
The above chiddush is based on a Mishnah in Succah (41a) and a Gemara in Menachos. The Mishnah teaches: התקין ר' יוחנן בן זכאי שיהא יום הנף כולו אסור – “R’ Yochanan ben Zakai made a takonah [enactment] that chodosh [new produce] is forbidden the entire day of the waving of the korban omer”. Rashi based on the Gemara in Menachos (68a) explains: When the Beis HaMikdosh was built, on the 16th of Nissan immediately after the korban omer was offered up, it was permissible to eat chodosh. When the Beis HaMikdosh was destroyed and there was no longer a korbon omer to be offered, chodosh was permissible already from sunrise on the 16th of Nissan.
The Gemara learns this from two seemingly contradictory pasukim. One pasuk says: עד עצם היום הזה – “(chodosh is prohibited) until the arrival of the day”, meaning, chodosh is already permissible from sunrise on the 16th of Nissan. Whereas another pasuk says: ד ע הביאכם - “(chodosh is prohibited) until the bringing of the korban omer”. These two pasukim seem to contradict each other, do we need to wait for the korban omer, or do we need to wait for sunrise? The Gemara answers: When the Beis HaMikdosh was built and a korban omer was offered up, chodosh was prohibited until after the korban omer, however, when it was destroyed and there was no longer a korban omer to be offered up, chodosh was only prohibited until sunrise.
However, R’ Yochanan ben Zakai came along and made a takonah, that even during the time of the churban, chodosh still remains prohibited the entire day. The Gemara explains, that the reason for this takonah is:משום שמהרה יבנה בהמ״ ק ויאמרו אשתקד מי לא אכל נו בהאיר מזרח השתא נמי ניכול ואינהו לא ידעו דאישתקד דלא הוה בהמ״ ק האי ר מזרח מ תיר השתא דאיכא בהמ״ ק עומר מתיר – “Because the Beis HaMikdosh will speedily be rebuilt (hopefully), and people will say, ‘last year we ate chodosh by sunrise of the 16th, therefore, this year as well we should be able to’. And people won’t realize that the only reason last year people were allowed to eat at that time was because there was no Beis HaMikdosh, however, this year that there is a Beis HaMikdosh and a korban omer, chodosh is prohibited until after the bringing of the korban omer.”
We see from the above that we must be consciously aware that, מהרה יבנה בהמ״ ק – “that the Beis HaMikdosh will speedily be rebuilt” The Zohar writes that Moshiach is destined to come on the Yom Tov of Succos. This is one of the reasons why Succos is known as Chag HoAsif, the festival of gathering. The Yom Tov of Succos is a time that is destined for Yidden from all four corners of the world to be gathered together.
Being that there is an obligation every single day to await the arrival of Moshiach and the rebuilding of the Beis HaMikdosh, and that Succos is a prime time for this to happen, the Binyan Shlomah says that one should make sure to pay for his arbah minim before Succos - even when the first day falls on Shabbos. In order to ensure that if the Beis HaMikdosh is built, they will be kosher for all seven days of Succos.
The Binyan Shlomah cites proof for his chiddush from one of the piyutim written by R’ Eliezer HaKalir. In the one of the piyutim we say: קיחתם בדמים יכשרו לשם איום ראויים להנטל בזה ראשון יום. The Binyan Shlomah understands this to mean: “Even though (when Succos falls on Shabbos) we won’t be taking the arbah minim on the first day, nonetheless, they should be fitting to be used on the first day, i.e. one should pay for them and ensure they are lochem [100% his]”.
However, the Binyan Shlomah concludes: “I am scared to say such a big chiddush, which I have not seen in any of the early or later poskim, however, I am simply coming to raise a point”.
