What was Heraclius's opinion of the Prophet Muhammad (saw) and his followers?
      Narrated 'Abdullah bin 'Abbas:                          I was informed by Abu Sufyan that Heraclius said to him, "I asked you      whether they (followers of Muhammad) were increasing or decreasing.      You replied that they were increasing. And in fact, this is the way of     true Faith till it is complete in all respects. I further asked you      whether there was anybody, who, after embracing his (the Prophets)      religion (Islam) became displeased and discarded it. You replied in      the negative, and in fact, this is (a sign of) true faith. When its      delight enters the heart and mixes with them completely, nobody can be     displeased with it."