Morals and Good Manners

Question: Are there (good) manners not mentioned in the Qur'aan and the Sunnah? And if so, how can we come to know of them?

The response: He (the Prophet,-- may AAllaah raise his rank and grant him peace) said:

"I have only been sent to complete upright moral character."

[found in Mushan Ahmad (2/381); al-Mustadrak (4280); al-Adab al-Mufrid (273); Shu'ab al-Eeman (7609); Sharh Mushkil al-Aathar (5194); on the authority of Aboo Hurayrah.]

The previous religions that Allaah legislated for HIs servants had also encouraged their followers to have virtuous manners. The people of knowledge mentioned that virtuous manners were sought from the followers of all previous legislations. And it is this perfect legislation that the Prophet (may Allaah raise his rank and grant him peace) came with that brings upright moral character to its completion and good manners to perfection.
Let us look at an example of that.

Qisas (retribution)

The people of knowledge have mentioned the issue of qisas which is when a person commits a crime against another: Is a punishment of the same nature of his crime to be applied to him or not? They have mentioned that this was something inflexible in the legislation of the Jews. They had to apply it, and the victims had no say in the matter (ie, they could not excuse the criminial). Later, it was the opposite for the Christians in their legislation. They were obliged to excuse the criminal in all cases.
Since holding the criminal accountable for his crime is something resolute that prevents recurrences of similar crimes, and since excusing him, on the other hand, is a kind of beautiful and praiseworthy act that can affect the criminal in a positive way, then our legislation has combined them both to make the affair complete, and for Allaah is the praise. The victim is given the right to excuse the criminal or hold him accountable. This way forgiveness is granted in its proper place, and retribution can take place when called for.

UPRIGHT MORAL CHARACTER, a Concise Guide to Attaining Dignified Islaamic Character
Shaykh Muhammad ibn Saalih al-Uthaymeen