I think it is more of a paraphrase than an actual quote. I think the actual quote you were thinking of is:You really ought to give credit when you quote someone. Or, if you don't know who to credit, at least put it in quote marks. This just looks like plagiarism.
With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg