Sforno on Genesis 47:31/ספורנו על בראשית מ״ז:ל״א

1השבעה לי!. This was only a device to enable Joseph to overcome objections by the Egyptians if they would not permit transfer of Yaakov’s remains to another country.

2וישתחו ישראל, to give thanks to His Creator for enabling him to exact this promise from his son.. We find that Eliezer, after hearing that Rivkah’s family agreed that he take Rivkah as a wife for Yitzchok, reacted in the very same fashion in 24,52 וישתחו ארצה לה', “he prostrated himself on the earth to G’d.”