The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Lech-Lecha (4), discusses the importance of personally involving oneself in Shabbat preparations (listen to audio recording for precise citation). He writes that even if a person has several servants capable of performing all the Shabbat preparations, he should nevertheless personally perform some action in preparation for Shabbat. The Ben Ish Hai points to numerous examples of Sages in the Talmud who performed certain tasks each Friday to prepare for Shabbat. Rabbi Hiya would cut vegetables; Rabba and Rav Yosef would chop wood; Rabbi Zera lit the fire; Rabbi Abba would fan the flames; Rav Papa made wicks; Rav Nahman cleaned the house.
The Ben Ish Hai adds that the perspiration that results from one’s efforts in preparing for Shabbat has the ability to atone for all sins. He also recalled the practice of his father to go to the fruit store each Friday to select choice fruits for Shabbat and bring them home.
The Arizal (Rav Yishak Luria of Safed, 1534-1572) instructed that all the food which one plans to use on Shabbat should be purchased specifically on Friday, so that it can be bestowed with the sanctity of Shabbat. However, the Ben Ish Hai writes that if Shabbat starts early Friday afternoon, such that there would not be enough time to prepare the food if it is purchased only on Friday, then foods requiring preparation may be purchased on Thursday. The exception, the Ben Ish Hai adds, is the Halot for Shabbat, which constitute the primary component of the Shabbat meals and must be baked specifically on Friday. The Ben Ish Hai rules that even if a person goes to the market every day to buy bread, he should bake Halot for Shabbat on Friday so that his wife can perform the Misva of "Hafrashat Hala" (separating part of the dough). He explains that Adam is called the "Hala of the world," the highest and most important creature, and he was created on Friday and committed his sin that day. It was Hava who caused him to sin, thereby ruining the "Hala of the world," and women rectify her mistake through the Misva on Hala. This should therefore be performed on Friday, the day when the sin occurred. For this reason, some women have the custom of designating some money for charity before separating Hala on Friday afternoon, in order to atone for Hava’s sin. Some women also set aside money for charity before lighting the Shabbat candles, which similarly serves to atone for Hava’s sin of "extinguishing the light of the world" by causing Adam to partake of the forbidden tree, thereby bringing death upon mankind. The charity is given before candle lighting in the hope of earning atonement for Hava’s wrongdoing.
It should be noted that the laws of Nidda also serve as a rectification of Hava’s mistake. The name "Hana" – which is spelled "Heh," "Nun," "Heh" – serves as a mnemonic for the three Misvot through which women atone for Hava’s sin: "Hala," "Nidda," and "Hadlakat Nerot."
Summary: There is a Misva to personally involve oneself in some aspect of the Shabbat preparations. Even a person who has hired help for the preparations should reserve some task for himself. It is preferable to purchase food for Shabbat on Friday, and not earlier, unless there would not be enough time to finish the preparation by the onset of Shabbat. One should bake Halot for Shabbat, and this should be done on Friday, and not earlier, since the Misva of separating Hala from the dough serves to atone for Hava’s sin, which took place on Friday.
