A.T. Robertson Commentary Romans 3:6

"God forbid: for then how shall God judge the world?" — Romans 3:6 (ASV)

For then how (επε πως). There is a suppressed condition between επε and πως, an idiom occurring several times in the N.T. (1 Corinthians 15:29; Romans 11:6,22). "Since, if that were true, how."