2
Mechilta dR Yishmael and more explicitly Mechilta dRashbi both make the point that from Moshe's honoring his father in law Yisro (Shemos 18:7) one sees that one ought to honor ones father in law as one honors ones father. Mechilta dR Yishmael (Shemos 18:17): מִכָּן אָמְרוּ, שֶׁיְּהֵא הָאָדָם מוּ...