Jamieson, Fausset and Brown on Genesis 41:40

40. Thou shalt be over my house--This sudden change in the condition of a man who had just been taken out of prison could take place nowhere, except in Egypt. In ancient as well as modern times, slaves have often risen to be its rulers. But the special providence of God had determined to make Joseph governor of Egypt; and the way was paved for it by the deep and universal conviction produced in the minds both of the king and his councillors, that a divine spirit animated his mind and had given him such extraordinary knowledge.

according unto thy word shall all my people be ruled--literally, "kiss." This refers to the edict granting official power to Joseph, to be issued in the form of a firman, as in all Oriental countries; and all who should receive that order would kiss it, according to the usual Eastern mode of acknowledging obedience and respect for the sovereign [Wilkinson].