רמב"ן — השבעה לי / וישבע לו

Q — Yaakov makes Yosef swear about burial in Cnaan, even after Yosef has already said 'אנכי אעשה כדברך'. Did Yaakov not trust his beloved tzaddik son?

A — Ramban: of course not — Yaakov never doubted Yosef. The shevua is diplomatic, not interpersonal: a precaution against Pharaoh. Pharaoh might refuse Yosef permission to leave Egypt — wanting Yosef close, or wanting a navi buried in his land for honor and merit. An oath ties Pharaoh's hands ('כי לא יהיה נכון להעבירו על שבועתו') and obligates Yosef to push harder for permission ('יצטרך יותר להשתדל בענין'). The strategy worked: Pharaoh's eventual approval cited exactly this — 'עלה וקבור את אביך כאשר השביעך.' Yaakov even worried the oath wouldn't suffice, so he later commanded all his sons regarding burial (49:29) — without making them swear, since that step was unnecessary at the family level. The chiddush: oaths can be tools of state diplomacy, not signals of distrust.