Adam Clarke on Exodus 18:19

I will give thee counsel, and God shall be with thee - Jethro seems to have been a man of great understanding and prudence. His advice to Moses was most appropriate and excellent; and it was probably given under the immediate inspiration of God, for after such sacrificial rites, and public acknowledgment of God, the prophetic spirit might be well expected to descend and rest upon him. God could have showed Moses the propriety and necessity of adopting such measures before, but he chose in this case to help man by man, and in the present instance a permanent basis was laid to consolidate the union of the two families, and prevent all future misunderstandings.