Q. Regarding the time of the Shabbos day seuda- is it OK to have a drink of water before davening and then start the seuda after chatzos? Or only b’dieved?
A. Shulchan Aruch (O. H. 288: 1) rules that it is prohibited to fast until chatzos on Shabbos. Therefore if one drank even water and certainly other foods, he is not considered as fasting. (See next questions as to what is permitted).
Rambam (H. Shabbos 30: 9) maintains that the second seuda of Shabbos should be before midday. Similar opinions are to be found in Sifrei Cabbalah (see Kaf Hachaim 291 : 2 quoting Zohar), Aruch Hashulchan (ibid. 2).
Bach (quoted in Mishna Berura (324: 2), seems to maintain that even after the fact one may not comply with the mitzva of the second seuda after chatzos. However, many Poskim disagree, as mentioned in Mishna Berura (288: 2) in the name of Eliahu Rabba, that one may be lenient when it is for the need of Torah learning or davening. (See Piskei Teshuvos 288: 1, that the six hours may be counted from the time one awakens).
On a similar question (1943) we answered: “Horav Shlomo Miller’s Shlit’a opinion is that on the onset, one should not wait to eat the seuda on Shabbos morning until after chatzos, even if one drinks something before.”
Horav Shlomo Miller’s Shlit’a opinion is that, one should on the onset eat or at least begin the day seuda of Shabbos before chatzos.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a