Rebbe Dovid'l of Tolna zt'l said that Shabbos Bereishis is הכנה על כל שבתות השנה, the preparation for all Shabbosim of the year. The Tzemech Tzedek of Lubavitz zy'a said, 'מ'שטעלט זיך אוועק זיך בראשית שבת אזוי גייט די גאנצע יאר, "How a person sets himself on Shabbos Bereishis, that is how it will be the entire year."
It states (2:3) וַיְבָרֶ ךְ אֱלֹק ִים אֶת יוֹם הַש ְּׁבִיעִי וַיְק ַדֵּש אֹתוֹ, "Hashem blessed the seventh day, and He made it holy." The Zohar (which people say Friday night before the seudah) teaches, "All brachos, above and below, come from the Shabbos." Shabbos is like a spring that gives brachos – ruchniyus and gashmiyus – to all worlds, above and below. The Zohar states wondrous brachos that we receive from the Shabbos, and in particularly, on Friday nights.
The Chofetz Chaim (al HaTorah) writes, "Those who lack emunah are so foolish. They come to Shabbos late and they are quick to leave the Shabbos. Behold the weekday was cursed with בזעת אפיך תאכל לחם, that they have to work hard to earn parnassah. Only Shabbos, alone, is freed from this curse. Hakadosh Baruch Hu, Himself, blesses this day, as Chazal say ברכו...וקדשו.... Instead of being wise and to come to Shabbos early to receive the brachos, and to leave Shabbos late, so they won't enter quickly into the curse of the weekdays, they do the opposite. They begin the brachos of Shabbos late, and they rush to leave it and to come quickly to the curses of the weekdays. Fortunate are those who understand this concept and accept Shabbos early and leave Shabbos late, so they can receive Hashem's brachos."
The Gemara (Kesubos 103a) states that after Rabbeinu Hakadosh was niftar, he would come every Friday night to his home and he appeared like a living person. He would make kiddush for his family. Reb Akiva Eigar (Gilyon Hashas) quotes the Sefer Chasidim (ז"תתשכ) "He came dressed in Shabbos clothes and he was motzi his family with kiddush. Unlike other dead people who are patur from mitzvos, the tzaddikim are alive after their demise, and they can make kiddush and be motzi others."
Nevertheless, we have to understand why specifically Rebbe was seen saying kiddush. This great level isn't written about any other Tana or Amora. Also, why did this revelation occur specifically on Friday night?
Ben Ish Chai (Ben Yehoyada) explains, "Hashem yisbarach doesn't hold back the reward from any being. Chazal (Kesubos 104a) tell us that all the chachamim of the generation were davening for Rebbe that he shouldn’t die. They prayed a lot, they cried, and they fasted, and they did this in large groups. This mass tefillah wasn't done for any other tzaddik before. In the end, Rabbeinu Hakadosh was niftar, but Hashem doesn't withhold reward, and the people who davened that Rebbe should live deserve reward. Hashem gave Rebbe permission to come to this world in a human body, so the bounty that Rebbe brought to his generation should continue, and it shouldn't stop after he was niftar."
This is because when a tzaddik is niftar, the great loss is that the bounty he brought to the world ends, however, "This time, he came to Olam HaZeh, and he sat among the living, so it isn't considered that he left the world. The shefa, bounty, that he would give to the world when he was alive continued even then."
Now, we understand the reason why Rebbe came to this world specifically on Friday night. That is the time when the bounty comes down to the world for the entire week.
