De Somniis (lib. i-ii)

And, moreover, he says to the wise Abraham, "that he will give him an inheritance of land from the river of Egypt to the great river, the river Euphrates," [*](Genesis xv. 18. ) not meaning a portion of the land so much as a better portion in respect of our own selves. For our own body, and the passions which exist in it, and which are engendered by it, are likened to the river of Egypt, but the soul and the passions which are dear to that are likened to the river Euphrates.

And here a doctrine is laid down, at once most profitable to life and of the highest importance, that the good man has received for his inheritance the soul and the virtues of the soul: just as, on the contrary, the wicked man has received for his share the body and the vices of the body, and those which are engendered by the body.