Why Moses Sent Zipporah Back on Aaron's Counsel

"And Jethro, Moses' father-in-law, took Zipporah, Moses' wife, after she had been sent away" (Exodus 18:2). Rabbi Yehoshua says: After he had dismissed her by word. Rabbi Elazar of Modi'in says: After he had dismissed her by a document. It says here "after she had been sent away," and it says elsewhere (Deuteronomy 24:1): "And he writes her a bill of divorce and gives it into her hand and sends her from his house." Just as the sending away mentioned elsewhere is by a writ, so too the sending away mentioned here is by a writ. When did he send her away? At the time when the Omnipresent said to Moses, "Go and bring Israel out of Egypt," he took his wife and his sons and set them upon the donkey. The Omnipresent said to Aaron, "Go out to meet your brother toward the wilderness." He went out to meet him and began to embrace and kiss him. Moses said to him: My brother, where were you all these years? He said to him: In Midian. He said: What is the nature of these people who are with you? He said to him: They are my wife and my sons. And he said to him: Where are you taking them? He said to him: To Egypt. He said to him: Over the first ones we are already grieving, and now you bring the latter ones? Immediately he said to her: Return to your father's house. Immediately she took her two sons and returned to her father's house. Therefore it is said "after she had been sent away, and her two sons."