ויענך וירעבך ויאכלך את המן אשר לא ידעת (ח-ג)
Moshe Rabbeinu tells Klal Yisroel, “Hashem gave you mann to eat, and you were afflicted and left hungry.” There is a Medrash Pliah on this posuk brought by the Chida ZT”L: "מכאן שמדליקין נרות בשבת". From this Medrash we learn that there is an obligation to light candles Friday night in honor of Shabbos. There are two questions here. First, what does eating the mann have to do with lighting candles for Shabbos? Second, if the mann had every taste a person could possibly want, why does the posuk say that they were afflicted and hungry? They should have been happy and satisfied with it!
The Rambam (הל' שבת) writes that the mitzvah of lighting candles is not a "רשות" (voluntary mitzvah) but a "חוב" (obligation), as it says "וקראת לשבת עונג". If a person sits at the Shabbos table and eats delicacies without seeing the food he eats, he has no pleasure or oneg. The food literally becomes an ענוי (torment). We learn this from the mann in the desert.
The gemara (יומא עד) asks, why does the Torah call the mann an "ענוי"? R’ Yosef answers that a person who sees the food he eats is no comparison to someone who eats his food without seeing it. This is exactly what the Yidden complained about in the desert: "בלתי אל המן עינינו" - in other words, although the mann had every taste, since they could not see actual food and all they saw was the mann itself, it was a torment. For this reason, there is a psak halacha that a blind person who is never satiated may not have to bentch. Why? Because the Torah says: "ואכלת ושבעת וברכת" - one must be “full” (שבע) in order to bentch.
This is the meaning of the Medrash Pliah. If the Torah calls the mann an "ענוי" because the Jews couldn’t see the actual food they were tasting, then it’s understood that if one sits at a Shabbos table without light and cannot see the food, he will not have oneg Shabbos and the food will become an "ענוי" - a torment for him. Thus, says the Chida: "מכאן שמדליקין נרות בשבת"