Rab objected to and refused to eat meat brought on a boat although he had never lost sight thereof.— Rabbi Johanan listened to a verse recited by a child; he took it as an omen and did not go to Bab3don to see Samuel after the death of Rab.
Rav Refuses the Meat and Rabbi Yochanan Hears the Omen
Gaster, Exempla of the Rabbis No. 273