Who was Jethro?
Jethro was Reuel's oldest son. Father-in-law of Moses, by whose counsel Moses chose chief men from the tribes to be rulers of thousands, hundreds, fifties, and tens, and to judge minor causes, reserving the weightier ones to himself (Exo. 18). "Jethro took a burnt offering and sacrifices for God," being a priest of the true God.
The primitive faith still had its representatives here and there in the Gentile world after Abraham's call, e.g. Jethro, and Melchizedek. Reuel's name, from El = God, implies he too was a God-worshipping priest-prince of his tribe, though the majority of the tribe bordering on the Hamite Canaan were idolaters (Exo. 2:16). Zipporah's repugnance to circumcision (Exo. 4:24-26) shows that it was not universal even among worshippers of the true God.
She circumcised the younger son only to save Moses from God's wrath, the elder was evidently already circumcised. Moses' delay in circumcising the younger was a sinful yielding to his wife. The occurrence induced him to send her back and his sons, and not take them to Egypt; Jethro brought them to him after Israel's arrival at Sinai.
Jethro of Midian (Abraham's descendant) celebrated a sacrificial meal with Aaron and Israel's elders; the representative firstfruits of the pagan who would afterward enter into fellowship with God and His people; as Amalek, another descendant of Abraham, represents on the contrary the pagan world hostile to the Lord and His people.
IBSE, "Isaac" (in the public domain) with minor edits.