He spoke, not by word of mouth, as the next verse showeth, but either by a letter, or by a messenger, as that word is used, Matthew 8:6,8, compared with Luke 7:3,6.
Related Commentaries of Exodus 18:6
Exodus 18:6
6 And he said unto Moses, I thy father in law Jethro am come unto thee, and thy wife, and her two sons with her.