In the Exodus narrative, Moses's father-in-law, the priest of Midian, is named Jethro.
Moses flees Egypt after killing an Egyptian and settles in Midian. There he helps the daughters of a Midianite priest, who is identified as Reuel in one passage and Jethro in others. Moses marries Zipporah, one of the priest's daughters, and becomes a shepherd for his father-in-law's flock. This period precedes the burning-bush call at Horeb.
After the Israelites leave Egypt, Jethro brings Zipporah and Moses's sons to meet Moses in the wilderness. He rejoices at Israel's deliverance and offers a sacrifice. Jethro then observes Moses judging disputes from morning until evening and advises him to appoint capable officials over groups of thousands, hundreds, fifties, and tens.
The names Jethro and Reuel create a well-known identification question. The text uses both names in connection with Moses's Midianite in-laws, and traditions explain their relationship in different ways. “Jethro” is the conventional answer to the wording about the priest who advises Moses.