CHAPTER No: 59
(Prohibition of evil thoughts regarding Allah)
Allah the Almighty said:
"They thought wrongly of Allah -the thought of ignorance. They said, 'Have we any part in the affair?' Say you (O Muhammad (May the peace and blessing of Allah be upon him) ): 'Indeed the affair belongs wholly to Allah.' They hide within themselves what they dare not reveal to you, saying: 'If we had anything to do with the affair, none of us would have been killed here.' Say: 'Even if you had remained in your homes, those for whom death was decreed would certainly have gone forth to the place of their death,' but that Allah might test what is in your breasts; and to Mahis that which was in your hearts (sins), and Allah is All-Knower of what is in (your) breasts."
Allah the Most Exalted said:
"Who think evil thoughts about Allah, for them is a disgraceful torment."
Ibn Al-Qaiyim (May Allah be pleased with him) said regarding the first verse: "The thought of ignorance is explained as meaning that Allah (May Allah be pleased with him) will not help the Messenger (May the peace and blessing of Allah be upon him) and his mission will soon fade away. It is also explained as meaning that the afflictions he suffered were not due to Divine Preordainment from Allah and His Wisdom. It is therefore explained as the denial of Wisdom and Decree and denial that the mission of His Messenger (May the peace and blessing of Allah be upon him) would be completed and that it would prevail over all other religions. These were the evil thoughts in the minds of Munafiqun (hypocrites) and Mushrikun (polytheists) which are mentioned in Surat Al-Fath as Su'-uz-Zan (evil thoughts). Su'-uz-Zan (evil thoughts) are against what is befitting the Most Perfect. Neither do they befit His Wisdom and Praiseworthiness nor His True Promise. Any person who thinks that the falsehood (Satan, polytheism etc.) will prevail over truth (Islamic Monotheism) continuously and it would cause truth to vanish; or who denies that things occur due to Allah's Decision and Decree; or who denies an overriding wisdom behind His Decree that is deserving of praise and thinks that such is due to an arbitrary purposeless will: these are the thoughts of those who disbelieve. Woe to those who disbelieve of the punishment of Hell.
"Most people think the worst of Allah with regards to what affects them in particular and what He does with others. No one is safe from that, except who truly knows Allah and His Names and Attributes, and the necessity of His Wisdom and Praise. Let the intelligent recipient of good advice look closely at himself in this matter and let him repent to Allah and beg His forgiveness for having harbored the worst thought about his Lord. If you were to look closely at (such individuals), you would see in him distress and annoyance with what Allah has decreed, blaming and finding fault in it, and thinking, it should rather be such and such. In this thought, some are up to lesser extent and others up to greater. Examine yourself: Are you free from such thoughts? If you are saved from it you have been saved from a great calamity. Rut if not, I cannot regard you as saved!"
Important issues of the Chapter
1) Explanation of the verse in Al-1mran (3:154).
2) Explanation of the verse in Surat Al-Fath (48:6).
3) Notice that the worst estimation of Allah (Su'-uz-Zan) is of uncounted variety.
4) Only the person who knows himself and (true meaning of) the Names and Attributes of Allah is safe from harboring such thoughts.
 This word Mahis has three meanings: (1) to test, (2) to purify, (3) to get rid of. (Tafsir Al-Qurtubi)