Q. Can one wish on Shabbos morning after davening a ‘Gut Shabbos,’ or is that improper? I have seen some people answer back, ‘A Gutn Erev Shabbos’ as if the salute they received was incorrect.
A. Horav Shlomo Miller’s Shlit’a opinion is that you may already wish a gut Shabbos on Friday morning, as the posuk says (Shemos 16: 5); ‘Vehoyo bayom hashishi veheichinu es asher yoviu. And it shall be on the sixth day as they prepare what they will bring.’ Shulchan Aruch (O.H. 250: 1), rules from Talmud (Shabbos 117: 2), that the preparations for Shabbos begin already on Friday early morning. That seems to have been also the minhag of Mori Verabi Horav Moshe Feinstein zt’l, (See Mekadshei Shevii p. 26).
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a