I don't know if the following is true, but the attribution to Flaubert sounds plausible.
***(1) "God is in the details."
It seems generally accepted that this was something said by the German-born architect Ludwig Mies van der Rohe (1886-1969) although almost certainly it was not invented by him. His obituary in The New York Times (1969) attributed the saying to him but it also appears to have been a favourite of the German art historian Aby Warburg (though E.M. Gombrich, his biographer, is not certain that it originated with him). In the form Le bon Dieu est dans le détail, it has also been attributed to Gustave Flaubert (1821-80). Subsequently, there has arisen the saying `The devil is in the detail' which has been described as a maxim of the German pop musician, Blixa Bargeld. He probably did not invent it himself as it is mentioned in Lutz Röhrich's Lexikon der sprichwörtlichen Redensarten (1994) - as `Der Teufel steckt im Detail'.*** (from http://www1c.btwebworld.com/quote-unquote/p0000063.htm)
Yoshie