Brachot 48 - When not to join in prayer
Earlier we learned that if three people ate together, they must invite each other for an after-meal prayer. This invitation is called "zimun." However, there are cases when they should not combine - such as when one of them ate food that was not kosher. A learned person should not join unlearned boors.
Who is considered a boor? - Anyone who does not say the Shema in the evening and in the morning - this is the definition of Rabbi Eliezer. Rabbi Yehoshua says, "Anyone who does not wear tefillin." Ben Azzai says, "Anyone who does not have tzitzit fringes on his four-cornered garment." Rabbi Nathan says, "Anyone who does not have a mezuzah on his home's entrance." Rabbi Nathan bar Yosef says, "Anyone who has children but does not raise them to study Torah." Others say, "Even if he learned the five books of the Torah and the clear rulings of the Mishna, he is a boor is he has not studied the Talmud" - and the accepted law is like these "others," which is a codename for Rabbi Meir.
Rabbi Ami said, "Two scholars and Shabbat complete a three-people quorum required for a common call to prayer (zimun)." But is Shabbat a person? - Rather, two scholars, if they sharpen each other intellectually (which is mostly manifest in a relaxed meal on Shabbat) complete a three-people quarum." Rav Chisda motioned, "Like me and Rav Sheshet," and Rav Sheshet indicated, "Like me and Rav Chisda."
King Yannai killed all the Sages, and there was no one left to say the after-meal prayer for him and the queen. His wife then made him swear that he won't harm a Sage, and called her brother, Rabbi Shimon ben Shetach, whom she had in hiding. They gave Rabbi Shimon a cup of wine, and he asked, "What do I say now? Blessed is the One Whose food Yannai has eaten?" Rather, he drank that cup, including himself in the meal, and proceeded to say the prayer with the next cup. The Talmud asks how he was allowed to do it, since he only drank but did not eat with them.
Art: John Francis - Still Life Fruit And Wine Glass