GEN634 As for exercising care in one’s thought and guarding it, you should not neglect to watch over your thoughts, reflections, and imaginings; for they alone are responsible – in proportion to their corruption or refinement – for most of the corruption or refinement in conduct, as it says in Scripture: “Above all that you guard, watch over your heart; for from it spring the sources of life Proverbs 4:23; For the devisings of man’s heart are evil from his youth [this verse]; For I know their devisings Deuteronomy 31:21; For Hashem searches all hearts, and understands the devising of every thought 1 Chronicles 28:9; It is a thing very close to you, in your mouth and I your heart, that you can do Deuteronomy 30:14; What does Hashem your God ask of you? Only that you fear God Deuteronomy 10:12.”  Therefore, my brother, see to it that all your actions are devoted solely to the Creator, may He be exalted, so that your work not be for naught and your labor not be in vain, as it is written: “Why pay money for no bread, and labor without being satisfied?” Isaiah 55:2  DUTIES 543