Musar su Salmi 128:2

From this episode we again learn that one must not rely on appearances, for even if someone appears blameless one never know what is in his mind.. The rule to remember is this: If someone refuses to benefit from the property of others — and needless to say from stolen property — and if he deals with others in good faith, then he is undoubtedly upright and honest. But if he kisses his tefillin while he prays but does not deal with others in good faith, then one must stay as far away from him as possible. For the main area in which fear of Heaven and righteousness are put to the test is with regard to money. Whoever stands firm in his righteousness in monetary matters can be considered truly righteous. Concerning him was it written, “When you consume the labor of your own hands” — that is, honestly — “fortunate are you” — in this world — “and it will be well with you” — in the World to Come, Amein.