Sir James George Frazer (1854–1941).  The Golden Bough.  1922.

§ 4. Osiris a God of the Dead
WE have seen that in one of his aspects Osiris was the ruler and judge of the dead. To a people like the Egyptians, who not only believed in a life beyond the grave but actually spent much of their time, labour, and money in preparing for it, this office of the god must have appeared hardly, if at all, less important than his function of making the earth to bring forth its fruits in due season. We may assume that in the faith of his worshippers the two provinces of the god were intimately connected. In laying their dead in the grave they committed them to his keeping who could raise them from the dust to life eternal, even as he caused the seed to spring from the ground. Of that faith the corn-stuffed effigies of Osiris found in Egyptian tombs furnish an eloquent and un-equivocal testimony. They were at once an emblem and an instrument of resurrection. Thus from the sprouting of the grain the ancient Egyptians drew an augury of human immortality. They are not the only people who have built the same lofty hopes on the same slender foundation.   1
  A god who thus fed his people with his own broken body in this life, and who held out to them a promise of a blissful eternity in a better world hereafter, naturally reigned supreme in their affections. We need not wonder, therefore, that in Egypt the worship of the other gods was overshadowed by that of Osiris, and that while they were revered each in his own district, he and his divine partner Isis were adored in all.   2