Forgot to recite Ritzei on Shabbos

Forgot to recite Ritzei on Shabbos: On Shabbos, one is required to mention the day of Shabbos [i.e. Ritzei] within Birchas Hamazon.[1] If one forgot to mention Ritzei in the Birchas Hamazon of the Friday night meal or the first Shabbos day meal[2], and only remembered after he already began […]