He was not satisfied with a simple promise from Joseph, that he would do his wish; he insisted upon his taking an oath by the sign of the covenant of Abraham, putting a hand under his thigh in accordance with the ceremony customary among the Patriarchs! But Joseph said: "Thou treatest me like a slave. With me thou hast no need to require an oath. Thy command sufficeth."
Jacob, however, urged him, saying: "I fear Pharaoh may command thee to bury me in the sepulchre with the kings of Egypt. I insist that thou takest an oath, and then I will be at peace." Joseph gave in, though he would not submit to the ceremony that Eliezer had used to confirm the oath he took at the request of his master Abraham. The slave acted in accordance with the rules of slavery, the free man acted in accordance with the dictates of freedom. And in a son that thing would have been unseemly which was becoming in a slave.