Imam Ali (peace be upon him): [In Irshad al-Qulub it is reported:] One night Amir al-Mu'minin (peace be upon him) was going from the mosque of Kufa toward his house, when a quarter of the night had passed. Kumayl ibn Ziyad, who was among the great and virtuous of the Shia and among the friends of that Imam, was with him. On the way they reached the door of a man who at that time of night was reciting the Qur'an with a sorrowful and pleasing voice, reciting the words of Allah the Exalted that are in the Qur'an: أَمَّنْ هُوَ قانِتٌ آناءَ اللَّیْلِ ساجِداً وَ قائِماً یَحْذَرُ الْآخِرَةَ وَ یَرْجُوا رَحْمَةَ رَبِّهِ قُلْ هَلْ یَسْتَوِی الَّذِینَ یَعْلَمُونَ وَ الَّذِینَ لا یَعْلَمُونَ إِنَّما یَتَذَکَّرُ أُولُوا الْأَلْبابِ [What! he who is obedient during hours of the night, prostrating himself and standing, takes care of the hereafter and hopes for the mercy of his Lord! Say: Are those who know and those who do not know alike? Only the men of understanding are mindful]. In his heart, Kumayl praised him and was pleased with his good state, but did not utter anything. Imam Ali (peace be upon him) turned to Kumayl and said: 'O Kumayl! Do not be impressed with this man's droning voice! For this man is of the people of the Fire, and soon I will inform you about his state.' Kumayl became bewildered and perplexed that Ali (peace be upon him) was aware of his inner thoughts and testified that this man, despite being engaged in worship and being in this good state [of intimate whispering] at this time of night, would be of the people of the Fire. Kumayl fell silent, but he remained in a state of astonishment, contemplation and thought about this affair. A long stretch of time passed from that incident until the state of the Khawarij changed and they fell into that condition [and became hypocrites and adversaries], and Amir al-Mu'minin (peace be upon him) fought them. This was while that group were memorizers of the Qur'an that had been revealed to the Prophet (peace be upon him and his family). On the battlefield, Amir al-Mu'minin (peace be upon him) turned to Kumayl, who was standing before Ali (peace be upon him) with his sword in his hand, and blood was dripping from that sword, and the severed heads of those disbelievers and transgressors had filled the ground. Ali (peace be upon him) placed the tip of his sword upon one of those heads and said: 'O Kumayl! أَمَّنْ هُوَ قانِتٌ آناءَ اللَّیْلِ ساجِداً وَ قائِماً [What! he who is obedient during hours of the night, prostrating himself and standing]; O Kumayl! This head is that very person who was reciting this verse on that night with a sorrowful voice, and you had been pleased with his state.' Kumayl kissed the feet of Amir al-Mu'minin (peace be upon him) and sought forgiveness from Allah, and sent blessings upon Muhammad and the family of Muhammad (peace be upon them) and upon Ali (peace be upon him), whose worth had remained unknown and hidden in society.