I heard the following explanation of this pasuk from the Admor of Pinsk-Karlin shlita, in the name of Rav Osher of Stolin zy’a:
It is known from the students of the Baal Shem Tov that there is tremendous spiritual benefit for chasidim to gather together and speak about matters related to avodas Hashem and chasidus, as well as the relate stories of tzadikim. (This is known by various names, such as ‘Sheves Achim’, ‘farbrenging’, ‘a zitz’ or ‘butteh’.)
This concept is hinted to in the words of the pasuk. It says that ‘you shall serve Hashem’ in the plural, indicating that when a group of people sit together, it is part of avodas Hashem.
Generally, when people gather together, refreshments are placed on the table, such as cake and herring. Some people cannot partake of the food and drink for health reasons, as they cannot tolerate sugar, salt or alcohol. Therefore, the pasuk says that Hashem will bless the bread and water, meaning that they will not harm anyone who partakes in them. This is because when one gathers for avodas Hashem, they will be healthy and will not be harmed by the food served at such gatherings.