'Ali, the "Lion of God," was once engaged in conflict with a Magian chief, and in the midst of the struggle the Magian spat in his face. 'Ali, instead of taking vengeance on him, at once dropped his sword, to the Magian's great astonishment. On his inquiring the reason of such forbearance, 'Ali informed him that the "Lion of God" did not destroy life for the satisfaction of his own vengeance, but simply to carry out God's will, and that whenever he saw just cause, he held his hand even in the midst of the strife, and spared the foe. The Prophet, 'Ali continued, had long since informed him that he would die by the hand of his own stirrup bearer (Ibn Maljun), and the stirrup bearer had frequently implored 'Ali to kill him, and thus save him from the commission of that great crime; but 'Ali said he always refused to do so, as to him death was as sweet as life, and he felt no anger against his destined assassin, who was only the instrument of God's eternal purpose. The Magian chief, on hearing 'Ali's discourse, was so much affected that he embraced Islam, together with all his family, to the number of fifty souls.
(Mathnavi of Maulana Rumi)