18:2 "After Moses had sent away his wife Zipporah" -
Calvin had "no doubt but that [Moses] underwent, together with his
family, that miserable yoke of bondage by which they were long oppressed, and
by this proof evidenced his faithfulness, so that greater authority might
attend his vocation," and Moses "sent away his wife to his father-in-law"
for a visit upon their arrival in Midian.
Pink sees an estrangement between Moses and Zipporah in
Exodus 4:25 when she
calls him a "bridegroom of blood". That results
in Zipporah going back to her father, as Israel's estrangement from
Jehovah began with "his blood be on us and on our children".