Prophet (a.s) recited the verse:“Is one whose heart God has opened to Islam, so that he has received enlightenment from God, (no better than one hard- hearted)?” [The Holy Quran: Zumar 39:22] and said: “When the light shines in the heart, it opens it and illuminates it.” He was asked: “O' Prophet of God! Is there any sign with which this can be recognized.” He said: “Abstaining from the world, and turning to the Hereafter, and being ready for death before it descends.”