Why do we cover the Hallah before Kiddush on Friday nights? TB Pesakhim 100

 Everybody on today’s daf TB Pesakhim 100 agrees that one should not begin a Shabbat meal close to minkha ketana, 2 1/2 hours after midday in order to eat the Sabbath meal with a hearty appetite. There is a disagreement between Rabbi Yehuda and Rabbi Yossei when a person begins a meal before the restricted time. Does he need to stop when it's dark, say Grace after meals, and begin a brand-new meal? Rabbi Yehuda says yes and Rabbi Yossei says the person doesn't need a hard stop. All he has to do is pause to say kiddush and then continue with his meal which automatically turns into a Shabbat meal.

Back during Talmudic times, people didn't sit around a large table. Imagine them reclining on a couch and a small table, like a TV tray, with food on it would be brought before each person. The following story is the source for covering the hallah before kiddush.

“Rabba bar Rav Huna happened to come to the house of the Exilarch. His hosts were reclining for a meal, and the attendants brought a table before him so he could eat as well. Since Shabbat had already started, he spread a cloth over the food and recited kiddush. That was also taught in a baraita: And the Sages agree that one may bring the table only if he has already recited kiddush; and if one brought out the table before kiddush, he should spread a cloth over the food and recite kiddush.” (Sefaria.org. translation)

Rashbam cites Rav Akhai Gaon in the Sheiltot rules we must first sanctify the Shabbat with kiddush and then bring out the TV tray tables with dinner in honor of Shabbat. If the tray tables are already in front of the guests, then you cover them with a tablecloth to pretend the food is not there yet. Once the tablecloth is in place, the person says kiddush.

Tosefot (ד"ה שאין) suggests two other reasons. First of all, they write the reality has changed. Like us, they had one large dining room table where everyone sat around. To remove the table before kiddush would be inconvenient at best and difficult or impossible at worst. To solve this problem they spread a tablecloth over the food as per our Gemara. The second reason they suggest that the covering of the hallah is a reminder of the miracle of the manna in the desert. A layer of dew was underneath the manna and a layer of dew was in top of it to form a protective cover. The tablecloth represents the dew.

There is a third reason. Halakha dictates a certain order when reciting more than one blessing. At a regular meal one says the blessing over the bread first and then says the blessing over the wine he wishes to drink with the meal. But on Shabbat the first thing we do before we sit down to the meal is to sanctify the day with kiddush wine. To preserve the order of the blessings, we cover up the hallah with a cloth and pretend it's not there. After we say kiddush, we uncover the hallah and say the motzi.