In the Hebrew Bible, Jethro visits Moses in the wilderness, gives advice about delegating judges, and leaves. The Targum Jonathan on (Exodus 18) transforms this administrative visit into a dramatic conversion story.
The Targum says Jethro announced to Moses: "I, thy father-in-law Jethro, have come to thee to be a proselyte; and if thou wilt not receive me on my own account, receive me for the sake of thy wife and of her two sons who are with her." This is a plea. Jethro was not casually visiting. He was asking to join the covenant, and he offered his family connection as leverage in case Moses hesitated.
Moses "came forth from under the cloud of glory" to greet him. The Targum specifies that Moses was living inside God's protective cloud, and he had to leave it to meet a non-Israelite. He then "kissed him and made him a proselyte." The Hebrew says Moses bowed and kissed him. The Targum adds the conversion, turning a greeting into a religious ceremony.
They entered "the tabernacle, the house of instruction," a detail absent from the Hebrew. The meeting happened in a place of Torah study, not just any tent. Jethro's famous theological declaration, "Now I know that the Lord is greater than all gods," gets a pointed addition in the Targum: "for by the very thing by which the Mizraee wickedly would have punished Israel by drowning them in the sea, upon themselves came the punishment." God used Egypt's own weapon against them. This is the Targum's principle of measure-for-measure justice.
Jethro's judicial advice also expands. He told Moses to teach the people "the prayer they are to offer in the house of congregation, the manner of visiting the sick, of burying the dead, of being fruitful in doing good." These are recognizable rabbinic mitzvot (commandments), projected into the wilderness. The chapter ends with Jethro departing and converting "all the children of his land." He did not just become a proselyte. He became a missionary.