Birkas HaMazon and Kos Shel Bracha

20. Drank wine during the meal. Some say that if one drinks wine during the meal but does not use a kos for Birkas HaMazon, his sin is too great to bear, as Hashem says, “He drinks wine to indulge his desires, but he does not use wine for Birkas HaMazon to honor Hashem” (רוח חיים פלאגי סי' קפ''ב ).

21. Shabbos. Some say that even if one is not careful to bentch with a kos during the week, he should be sure to bentch on a kos for all three seudos (אליה זוטא סי' רפ''ט בשם השל''ה, סדר היום קידוש ד''ה ואח''כ, מקור חיים רע "ד, משמעות ערוה''ש קפ "ב ס''א ). This is particularly true based on the opinion we cited (above, 20) that when there is wine on the table, one should make sure to bentch with a kos.