One of the most definite aspects of the Muslim way of speaking is the scrupulous observance of the boundaries between the lawful and the unlawful as prescribed in the Qur'an. With the verse, "Those who repent, those who worship, those who praise, those who fast, those who bow, those who prostrate, those who command the right, those who forbid the wrong, those who preserve the limits of Allah: give good news to the believers." (Surat at-Tawba: 112), Allah commands adherence to these limits.
Just as believers seek to avoid that which Allah has prohibited, and carry out that which He has commanded, they must also observe the same bounds in their speech throughout their lives. They must not defend in word or support any behavior which Allah has commanded them to renounce. They should also speak in praise of behavior which Allah approves of. For example, believers know that Allah disapproves of and has forbidden depriving others of their rights, making an unfair profit by the fraudulent weighing of goods, lying and bearing false witness, and for that reason do not tolerate such things. They cannot offer tacit support by remaining silent when confronted with one who defends sinful behavior. They do not hold back from saying what is true and right; on the contrary, they take great pleasure in explaining the morality related in the Qur'an to others. He never gives way to such thoughts as "If I oppose their ideas, will they take action against me?" or "I wonder what they think of me?," thus remaining silent, because, as we are informed in the verse, "It is a Book sent down to you—so let there be no constriction in your breast because of it—so that you can give warning by it and as a reminder to the believers." (Surat al-A‘raf: 2) it is incumbent upon believers to admonish others based on the Qur'an. For this reason, they explain to others their errant thinking and expound to them instead what is correct, using evidence from the Qur'an. By explaining that certain behavior is disliked and prohibited by Allah, they invite others to observe the limits set by Him. On realizing that those with whom they are talking will not heed the advice, realizing instead that they are blaspheming the Qur'an, they obey Allah's commands by abandoning such people. Allah relates in the Qur'an as such:
When you see people engrossed in mockery of Our Signs, turn from them until they start to talk of other things. And if Satan should ever cause you to forget, once you remember, do not stay sitting with the wrongdoers.
In another verse, we are told that when the faithful come face to face with people speaking ignorantly, they are honorable and respectful, and pass on saying salaam (peace):
The servants of the All-Merciful are those who walk lightly on the earth and, who, when the ignorant speak to them, say, "Peace." (Surat al-Furqan: 63)
