We are informed in the Qur'an that Allah considers people's hearts, as He reveals in " The day when wealth and sons avail not (any man) Save him who bringeth unto Allah a whole heart " (Qur'an, 26,27:89)

 But the Qur'an's concept of a "sound heart" is not only the pureness of heart that some people understand it to be. People who believe themselves to possess moral excellence because "they do not mean any harm to people" or "now and then they help the needy" only deceive themselves, but, for the Qur'an defines a sound heart as turning to and submitting fully to Allah. Some people are believed to have a sound heart because they feed stray dogs, smile at neighbors, or sometimes help the needy. But being saved from Hell and earning Allah's good pleasure and mercy require far more than being known as a "good person": One must be the type of believer described in the Qur'an. An act or an attitude that is accepted as a good deed by a society ignorant of religion, although it is not based upon the Qur'an's values, may not be worthy in Allah's sight. The main criterion that renders a deed good and worthy in His sight is the degree of its conformity with the Qur'anic criteria. The following verses are quite explanatory:

Do you make the giving of water to the pilgrims and looking after the Masjid al-Haram the same as believing in Allah and the Last Day and struggling in the Way of Allah? They are not equal in the sight of Allah. Allah does not guide wrongdoing people. (Qur'an, 9:19)

 It is not devoutness to turn your faces to the East or to the West. Rather, those with true devoutness are those who believe in Allah and the Last Day, the Angels, the Book and the Prophets, and who, despite their love for it, give away their wealth to their relatives, to orphans and the very poor, to travelers and beggars, to set slaves free, and who establish prayer and pay alms; those who honor their contracts when they make them, and are steadfast in poverty and illness and in battle. Those are the people who are true. They are the people who have taqwa [consciousness of Allah]. (Qur'an, 2:177)

People with sound hearts, in the Qur'anic sense, have faith in Allah, observe the limits and prohibitions that He has established, and submit to Him fully. In the Islamic sense, there is no other form of a sound heart, for the Qur'an defines a person with a sound heart as someone who constantly brings Allah to mind and feels at peace with His remembrance. The following verse makes this quite clear:

 Those who believe and whose hearts find peace in the remembrance of Allah. Only in the remembrance of Allah can the heart find peace. (Qur'an, 13:28)

 In another verse, Allah describes believers as those "whose hearts quake at the mention of Allah" (Qur'an, 22:35). In yet another verse, He states: "Has the time not arrived for the hearts of those who believe to yield to the remembrance of Allah and to the truth He has sent down?" (Qur'an, 57:16)

 This sensitivity of the heart is what enables believers to derive pleasure from the Qur'an's morality and to feel a great pleasure and peace in obeying Allah. Allah describes this sensitivity as "Allah's guidance":

 Allah has sent down the Supreme Discourse, a Book consistent in its frequent repetitions. The skins of those who fear their Lord tremble at it, and then their skins and hearts yield softly to the remembrance of Allah. That is Allah's guidance, by which He guides whoever He wills... (Qur'an, 39:23)

Consequently, a sound heart in the Islamic context means a heart that is purified from all forms of impurity that draw one away from Allah. Such people stay away from worldly greed, selfishness, fears, and insecurity. As a result, they do not become attached to any person or thing other than Allah or feel a type of love for them that is independent of Allah.

 In brief, people cannot have a sound heart if they do not obey Allah and do not fulfill the requirements of Islam. Those who claim to have a pure heart and thus consider it unimportant to comply with Islamic principles may assume that they deceive Allah and believers. But in fact, they only deceive themselves, and their self-proclaimed pure heart only indicates the insincerity of a person who avoids fulfilling his or her religious acts of worship and presents a flawed way of life as Islam. Such insincerity is not accepted either in Allah's sight or in the eyes of Muslims.