The mind is an essential means in religion, and the number of the Ayat in the Quran in which the mind is mention is close to 1000. Since the mind differs from a person to another, it should base its judgment on facts only, simply because some people use their mind to justify their deeds which are motivated by desires and interests, and I will talk about this in details.

 This crucial device (i.e. the mind) is Divinely tuned to be congruent with Share' (Islamic laws) 100 %, because this Share' is from Allah, and the mind is created by Allah as well, and since both of them come from One Origin (i.e. Allah) they must get along with one another.

 Man is created to live in this evanescent worldly life, but he should prepare for the eternal one (i.e. the Hereafter). Man's nature urges him to enjoy the worldly life at the cost of losing the Hereafter, whereas his mind entails seeking the Hereafter, so that man can rejoice the eternal happiness in Allah's Paradise. Scholars said, "Whoever strives for the worldly life and is forgetful of the Hereafter is insane." Hence, even if man is highly educated, his education is the outcome of mere intelligence, and it has nothing to do with reasoning, for when he overlooks the great truth in this universe, the Hereafter and the purpose of his existence, he turns into an insane man. Allah says:

﴾Nun. [These letters (Nun, etc.) are one of the miracles of the Qur'an, and none but Allah (Alone) knows their meanings]. By the pen and what the (angels) write (in the Records of men)* You (O Muhammad PBUH) are not, by the Grace of your Lord, a madman.﴿

[Al-Qalam, 1-2]

 You should believe in every atom in your body that the person who deserts praying, who does not know Allah, who is indulged in sins, who extorts people's money and who assumes that he is sane (after all that), is insane and an idiot even if he acquires the highest scientific degrees. This man is stupid, because he is oblivious of the fact that he will be called to account for every single deed he performs:

﴾So whosoever does good equal to the weight of an atom (or a small ant), shall see it* And whosoever does evil equal to the weight of an atom (or a small ant), shall see it. ﴿

[Az-Zalzalah, 7-8]

Allah has created man's mind to be essential in religion:

 The prudent, on the other hand, lives a quiet, peaceful and happy life, simply because he never takes what does not belong to him, but he takes only what belongs to him, he knows his limits and he builds his relations on clear ground. As a result, he gains people's love, he earns lawful money, he starts a family and he raises his children religiously. He uses his mind for the purpose of the Hereafter, and so he gains it, but at the same time he gains the worldly life for the same reasons.  The Prophet PBUH said:

((Mas has not been given a more precious gift than the reason with which he is guided to the Right Path and is kept away from that which causes his doom. Man's faith and religion will not be complete unless his reason brain becomes mature.))

[Al-Baihaqi in Shu'ab Al-Iman by Umar]

 The prudent is pleased, and he makes other people pleased too,, whereas the unwise fool spreads miser and is miserable himself. The mother of the Divine Graces is to have a prudent mind and a wise judgment with which one can manage his life among people and is able to gain their love. Only then, he will be happy with an ordinary wife and limited income, but lacking reason and wisdom will make man miserable even if he has the most beautiful wife and unlimited financial means.

 Let me tell you the story of the Companion Na'eem Ibn Mas'ood who was one of the notable Companions. Before embracing Islam, he was the leader of Ghatafan tribe, and he declared the war against the Prophet, peace be upon him, and was among the pagans in Al-Khandaq Battle (trench battle), but when he was alone in his tent he thought to himself in a monologue, which was a turning point in his life. He said, "Woe on you Na'eem! Why are you here? What brought you from the distant lands of Najd to fight this man (Muhammad, peace be upon him) and his followers? What did he do? Did he rape women? Did he steel? Did he kill anyone? No, by Allah, he did not." He went on saying, "O, Na'eem, where is your reason, do you want to fight him for no reason? Does it befit your prudence to fight and kill or get killed for no reason?" "Woe on you O Na'eem, what makes you draw your sword in the face of this righteous man who orders his followers of justice, benevolence and maintaining kin ties?" "Woe on you O Na'eem, what pushes you to be involved in the blood of his companions who followed the guidance and the truth this man put forth?"

 Because of that minute of deep righteous thought, he acquired happiness forever and ever. Unlike him, lots of people died as polytheists not because they adopted the ideology of polytheism, but because they followed sh3er (who were polytheists) and never thought of adopting their own ideology.

 Na'eem's monologue had to come to a conclusion which was to take the decision of embracing Islam and to carry it out right away. He sneaked out of his tent in the dark and headed to the Prophet's camp and stepped into his tent, which took the Prophet, peace be upon him, aback, as one of the enemies' leaders was inside his tent, so He said in surprise, "Na'eem!!!" To which Na'eem answered, "Yes, it is me." The Prophet, peace be upon him, asked, "Why are you here?" Na'eem said, "I came to bear witness that there is no Deity worthy of worship but Allah and that you are His Slave and Messenger, and that you came with the truth. Then he continued, O Prophet, I embraced Islam, and my people do not know that yet, so order me, and I will carry out your order."

 The Prophet PBUH was facing 10.000 men with their fatal weapons, the Jews broke their covenant with the Prophet, and the end of Islam was a matter of hours, so what can one man (Na'eem bin Mas'ood) do? The Prophet, peace be upon him, asked him to sow dissension among the enemies, he said, "You are one man only and you will make much difference here, so go to your people and sow dissension, for war is a trick." At that point, Na'eem decided to use his shrewdness, his big mind, his intuition, his intelligence and all his clever ways to serve the new religion he embraced. Na'eem said, "I will do so O Messenger of Allah, and you will hear good news soon if Allah wills."

 Because of that minute of deep righteous contemplation, he became another man and moved from being a Kafir to a notable Companion who fought with the Prophet PBUH and was a reason of defeating the Kuffar. He went back to Quraish and he sowed dissension between them and the Jews who broke their covenant with the Prophet PBUH. He said to Quraish, "The Jews regretted breaking their covenant with Muhammad, and they are about to ask you for hostages to make sure that you will not walk out on them only they will give these hostages to the Prophet to kill them". Then he said to the Jews, "Ask Quraish for hostages", and by that he sowed dissension between Quraish and the Jews. During the battle Allah sent the fierce wind which overthrew their pots, put out their fires and uprooted their tents, and Allah sufficed for the believers in the fighting.

[This story is mentioned in details by Ibn Hijr in Fath Al-Bari]

 Man should make soul searching and should reckon himself asking if his job is unlawful, if there is a sin committed in his household, if his wife is non-religious or if his children are not raised according to Islam. In this soul searching one should ask himself (just like Na'eem), does it befit me as a Muslim to disobey Allah? Does it befit me to do this or to do that? The Prophet PBUH said:

((Everything that is done has a backbone, and the backbone of man's deeds is his reason. The healthier man's reason is, the better his worship to Allah will be))

[Al-Firdaws bi Ma'thoor Al-Khitab by Abi Sa'eed]

 Have you not heard what the wicked disbelievers say?

﴾And they will say: "Had we but listened or used our intelligence, we would not have been among the dwellers of the blazing Fire!"﴿

[Al-Mulk, 10]

 Where are the Companions who believed in the Prophet PBUH, who sided by him, who supported him, who followed the Light revealed to him and who fought with him, now? They are in the highest ranks. Whenever one of the Companions is mentioned every Muslim since Islam till the end of days but says, "May Allah be pleased with him." Does anyone say the same when Abu Jahil is mentioned, may Allah, the angels and all people curse him till the Day of Resurrection? Abu Jahl and the like of him were enemies of the truth, so they deserved to be cursed in the worldly life and in the Hereafter, because they did not use their minds, but rather they followed the mob, the traditions and the conventions just like so many sh3er who live their moment, but how about? Are you with the majority mob or with the believing, prudent and shrewd minority?

 Our master Ali, may Allah be pleased with him, said, "O son, there are three kinds of people: one kind is of those learned people who are highly versed in the ethics of truth and philosophy of religion, second is the kind of those who are acquiring the above knowledge and the third is that class of people who are foolish. They follow every pretender and accept every slogan, they have neither acquired any knowledge nor have they secured any support of firm and rational convictions. Beware Kamil that you will not be like anyone of them." Our master Umar, may Allah be pleased with him said, "Man's origin is his mind, his religion is his kin and his good conducts are his chivalry."

 Al-Hasan Al-Basri said, "Allah granted man mind which is his rescuing means s one day." A writer said, "Man's mind is his best friend, whereas ignorance is his enemy, and there is no graver enemy to man than ignorance." We might have enemies, but our ignorance is the fiercest enemy, because "the ignorant man harms himself in ways which even his enemies will not harm him with." Hence, the mind is man's best friend, whereas ignorance it his worst enemy. Others said, "The best skill is the mind, and the worst disaster is ignorant." A poet said:

The sound mind exalts man among people
though his financial means might be tight
And the feeble mind degrades man among people
though his bloodline and ancestry might be honorable
Man lives amongst people due to the state of his mind
for it is the backbone of his knowledge and experience
The best Divine Grace granted to man is his mind
for nothing is even as precious as it is
When Allah the Most Gracious gives man a sound mind
Man will be able to acquire good conducts and goals