Avot D'Rabbi Natan 16

 

When a man stirs up his passion and is about to commit an act of lewdness, all parts of his body are ready to obey him. On the other hand, when a man is about to perform an act of piety, all his parts become laggard, because the impulse to evil in his innards is ruler of the two hundred and forty-eight parts of his body, whereas the impulse to good is like a man confined in a prison.