Sefer Tiferes Shmuel explains this pasuk by quoting the Mishnah (Shabbos 14:3) that says that “one may eat any food for a refuah on Shabbos.” He explains that source of refuah is created on Shabbos, through the “yichudei ha’olamos” that are made when one eats Shabbos foods with the proper kavanos. For this reason, Chazal say (Shabbos 12B): “It is Shabbos, when we refrain from crying (to Hashem) but the refuah is close to arriving.” He says that this is hinted to from the words “rak shivto yitzein v’rapo yerapeh” – through the holiness of eating on Shabbos, one is healed.”
Sefer Mofes Hador (Chelek 1, pahe 410) brings the following incredible story:
One of the distinguished chasidim of Kerestir was the philanthropist, R’ Yosef Shraga of Budapest zt”l, who donated much charity towards the needs of the court of Rav Shayala zy”a. R’ Yosef once suddenly became ill and seemed close to death. His son, R’ Chaim zt”l, immediately traveled to Kerestir and told the Rebbe that his father’s life was in danger.
This occurred on a Friday. At the time of R’ Chaim’s arrival, Rav Shayala still didn’t have enough money to buy Shabbos food for the guests who were going to be eating in his home. He said to R’ Chaim, “Don’t worry. If you sponsor the food for this Shabbos, your father will be healed. By the time you get home, you will find your father completely healthy.”
R’ Chaim was amazed to hear this, but Rav Shayala told him, “Why are you so surprised? The pasuk says: ‘Rak shivto yiten v’rapo yerapeh.’ Just give Shabbos, and the sick man will be healed in that merit.”
R’ Chaim gave Rav Shayala a large sum of money, which was used for the Shabbos food. When he got home, he found his father completely healed.
