With the Pharaoh out to get him, Moses flees for his life. He marries the shepherdess Zipporah, daughter of the priest of Midian. They have two sons: Gershom and Eliezer.
Years later when Moses and his family travel to Egypt, God afflicts Moses. This is apparently because Moses had not circumcised his son Gershom, as God commanded the Israelites to do through Abraham.
Just as God is about to kill Moses, Zipporah takes decisive action, circumcises Gershom, and touches Moses with the removed skin. This appeases God and Moses is spared.
Zipporah does what her husband did not do, she obeys God’s command, and saves her husband’s life.