Wisdom from the Early Cynics, Diogenes 23

When Lysias the druggist asked Diogenes if he believed in the gods, "How can I help believing in them," he said, "when I see a god-forsaken wretch like you?" Others give this retort to Theodorus. 

Seeing someone perform religious purification, he said, "Unhappy man, don't you know that you can no more get rid of errors of conduct by sprinklings than you can of mistakes in grammar?" 

He would rebuke men in general with regard to their prayers, declaring that they asked for those things which seemed to them to be good, not for such as are truly good.  

As for those who were excited over their dreams, he would say that they cared nothing for what they did in their waking hours, but kept their curiosity for the visions called up in their sleep. 

—Diogenes Laërtius, 6.42-43