Surah Yunus, Ayat 40-41

Ayat 40. And of them there are some who believe therein, and of them there are some who believe not therein, and your Lord is All-Aware of the Mufsidun (evil-doers, liars, etc.).

Ayat 41. And if they belie you, say: "For me are my deeds and for you are your deeds! You are innocent of what I do, and I am innocent of what you do!"

Hazrat Nawwas bin Sam`an (May Allah be pleased with him) reported: I asked Messenger of Allah  [SAWW](PBUH) about virtue and sin, and he said, "Virtue is noble behaviour, and sin is that which creates doubt and you do not like people to know about it.'' [Muslim Hadith # 6195].  

Lesson : as mentioned above in Surah Yunus Ayat 41. "And if they belie you, say: "For me are my deeds and for you are your deeds!"  An important principle enshrined in this Hadith says that courtesy is a virtue, because a refined mind cultivates good habits, performs good deeds, and shuns all that is bad and corrupt. Also, a simple and understandable principle is laid down about sin. Man feels the pricking of conscience over every bad deed and is also afraid of the reproach of fault-finders, provided he has not reached the lowest point of moral depravity. But a seared conscience is least disturbed even by a heinous and deadly sin or by public censure. We can understand it by the example of man's smelling sense. If it is not dead, man can feel a stink and repugnant odour. But a long association with a dung heap robs away one's smelling sense and feeling of refuse.