The Torah states that Yithro "took Tzipporah, Moses' wife, after she had been sent" (Exodus 18:2). The phrase "after she had been sent" is vague — sent where? By whom? Under what circumstances? Rabbi Yehoshua resolved the ambiguity with a bold legal claim: Tzipporah had been sent away with a divorce.
Rabbi Yehoshua's proof relied on a technique called gezeirah shavah — linking two passages that share the same key word. The word here is "sending" (shiluchim). In (Exodus 18:2), Tzipporah is described as having been "sent." In (Deuteronomy 24:1), the Torah uses the same word for divorce: "and he shall send her from his house." Rabbi Yehoshua argued: just as "sending" in Deuteronomy means a formal divorce with a get (a written bill of divorce), so too "sending" here means Moses had formally divorced Tzipporah.
The implication is extraordinary. At some point during the tumultuous events of the Exodus — the plagues, the departure from Egypt, the journey to Sinai — Moses had given his wife a get and sent her back to her father's house. Yithro then brought her to the wilderness camp, along with their two sons, to reunite the family.
The Mekhilta does not explain why Moses divorced Tzipporah, and the silence is deliberate. The teaching focuses on the legal mechanism, not the emotional story. But the reader cannot help wondering: what was it like for the greatest prophet in history to hand a bill of divorce to his wife? And what was it like for Tzipporah to return to him in the desert, carrying a document that said their marriage had ended?