Bg 18.31

yaya dharmam adharmam ca
karyam cakaryam eva ca
ayathavat prajanati
buddhih sa partha rajasi

Word for word: 
yaya — by which; dharmam — the principles of religion; adharmam — irreligion; ca — and; karyam — what ought to be done; ca — also; akaryam — what ought not to be done; eva — certainly; ca — also; ayatha-vat — imperfectly; prajanati — knows; buddhih — intelligence; sa — that; partha — O son of Prtha; rajasi — in the mode of passion.

Translation: 
O son of Prtha, that understanding which cannot distinguish between religion and irreligion, between action that should be done and action that should not be done, is in the mode of passion.