He knew that the Prophet (S), loved and respected Abu Dharr Ghifari. But as he was stationed far away, it was not possible to benefit from the presence of Abu Dharr. So he wrote a letter. In this letter he sought from Abu Dharr, counsel and admonition which would guide him in his behaviuor.
Abu Dharr wrote back: Do not be an enemy of whom you love most.
And as he went through the reply, he was disappointed. What did Abu Dharr mean? How would one ever act as an enemy to the most beloved? But on the other hand, he thought, Abu Dharr was no ordinary person. There must be a deeper meaning, so he wrote to him again seeking explanation.
'The meaning is quite simple', Abu Dharr wrote, 'To every living being the most beloved is its own self. To you, your self is the most beloved and when I admonished you not to act as an enemy, I meant do not be your own enemy. Remember when a man commits a sin, and acts contrary to the behests of Allah, he harms himself.'