Whatsoever then ye have well in this world, when ye recollect to have done any thing good, be very fearful about it, lest the prosperity granted you be your recompense for the same good. And when ye behold poor men doing any thing blameably, fear not, seeing that perhaps those whom the remains of the slightest iniquity defiles, the fire of honesty cleanses.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: in Hom. 40.