What does Exodus 4:18 mean?
Having encountered the Lord (Exodus 3:4–6), received his mission (Exodus 3:10), and been given answers to his concerns (Exodus 4:8–9, 14), Moses takes the first steps in returning to Egypt. He'd left under bad circumstances (Exodus 2:11–15) and spent many years creating a life and family in exile (Exodus 2:21–22). This task will disrupt that new life. So, Moses begins by speaking to the leader of his new family group: his father-in-law. The names Jethro and Reuel are both referred to as the priest of Midian (Exodus 2:18; 3:1). These appear to be the same person; several characters in the Bible are known by more than one name (Genesis 17:5; 32:28; Daniel 2:26; Acts 13:9).Moses requests to leave his duties towards the family while he is gone. He says he is going to check on the welfare of his people—this is not a lie, but it certainly leaves out major details. Most likely, Moses didn't feel his father-in-law was ready to hear about this supernatural encounter.
Jethro's response shows that he trusted his son-in-law. As far as we know from Scripture, this is the last time they will see each other until Moses is leading the people of Israel across the wilderness (Exodus 18:6–7).