In Book 2, Chapter 14 of Nishmat Hayyim, Menasseh ben Israel cites a comment on Genesis 6:6. The Biblical text is "And God regretted that he had made man on the Earth," and the comment is
"When God sent the soul, which is called 'Man,' from its glorious rest down to the land of darkness and the shadow of death, it was joined with the body and sinned and ended up in the dust."
Contrary to his usual practice, Menasseh does not cite the source. Does anyone know where it comes from?
University of Arkansas