Heart, Self & Soul: The Sufi Psychology of Growth, Balance, and Harmony, Robert Frager, Quest Books, Theosophical Publishing House, p.  129

When Muhammed and the early Muslims were returning from a major battle ...

Robert Frager

When Muhammed and the early Muslims were returning from a major battle, he turned to his companions and said, "Now we are leaving the lesser jihad and going to the greater jihad." The warriors were stunned by his words. They were exhausted, their arrows were gone, their swords and lances were blunted or broken. The Prophet went on, "The greater jihad is the battle with what is in your breasts!"

The translation of jihad as "holy war" is misleading and usually inaccurate. Muslim leaders have often called their wars jihad, meaning God was on their side. The basic Koranic meaning of jihad  is "struggle," and most often refers to struggle '"in the path of God." The basic practices of Sufism - remembrance, service, contemplation - all involve struggle. They take energy, commitment and will power.