Mishnà su Isaia 30:78

Rabbi Shimon said: if three have eaten at one table and have not spoken there words of Torah, [it is] as if they had eaten sacrifices [offered] to the dead, as it is said, “for all tables are full of filthy vomit, when the All-Present is absent” (Isaiah 28:8). But, if three have eaten at one table, and have spoken there words of Torah, [it is] as if they had eaten at the table of the All-Present, blessed be He, as it is said, “And He said unto me, ‘this is the table before the Lord’” (Ezekiel 41:22).