The sage known for his extraordinary carefulness was Rav, and his caution extended even to the smallest details of daily life. The Talmud in Hullin (95b) preserves a teaching about his approach to signs and omens that reveals just how seriously the rabbis took the line between wisdom and superstition.
Rav was traveling to visit a community in a distant town. Along the way, he encountered a series of small incidents—a bird flew across his path from right to left, a dog barked three times, a stranger's donkey refused to move from the road. In many ancient cultures, these would have been read as omens, signs from the heavens to turn back or press forward.
Rav paused. He was no superstitious peasant, but neither did he dismiss the natural world as meaningless. The Torah itself warned against divination (Deuteronomy 18:10), yet the sages also recognized that God sometimes communicated through the fabric of daily events.
His decision was characteristically careful. He would not change his plans based on signs alone, but he would proceed with heightened awareness. "A person should not rely on omens," he taught, "but neither should a person ignore the whisper of caution in his own heart."
The Midrash HaGadol on Genesis, in the portion of Chayei Sarah, expands on this principle. When Abraham's servant Eliezer sought a wife for Isaac, he devised a test involving water and camels (Genesis 24:14). Was this divination? The sages said no—it was careful observation of character. Carefulness meant using every available means to make wise decisions while refusing to surrender reason to superstition. The boundary was thin, but the careful person walked it with steady feet.