Pesach - Pouring the Fifth Cup – Understanding the Rambam and Kos Shel Eliyahu - כוס חמישי

From Rulings and insights from the Lubavitcher Rebbe - Rabbi Chaim Wolosow by R Chaim Wolosow.

After the four cups, one may not drink further, even water. The Rebbe explains the Rambam’s view of pouring a fifth cup without drinking—either as a compromise with Rabbi Tarfon or as an added practice—and distinguishes it from the communal Kos Shel Eliyahu. https://www.torahrecordings.com/shulchan_menachem/orach_chayim/244