Ante-Nicene Fathers, Vol VIII:
Pseudo-Clementine Literature.: Chapter XXXI

p. 291 Chapter XXXI.—“What Do Ye More Than Others?”

“But some one of you will say, Must we then do whatsoever things we did while we were idolaters?  I say to you, Not all things; but whatsoever you did well, you must do now, and more:  for whatsoever is well done in error hangs upon truth, as if anything be ill done in the truth it is from error.  Receive, therefore, from all quarters the things that are your own, and not those that are another’s, and do not say, If those who are in error do anything well we are not bound to do it.  For, on this principle, if any one who worships idols do not commit murder, we ought to commit murder, because he who is in error does not commit it.