In the name of Allah, Most Gracious, Most Merciful
"It was by the mercy of Allah that you were gentle with them (O, Mohammad) for if you had been harsh and hard of heart they would of dispersed from around you. So pardon them and pray forgiveness for them and consult with them in the affair" (Quran 3:159).
This verse from the Holy Quran indicates that Prophet Mohammad's (saw) attitude was a factor in attracting people to Islam. Any leader who wants to summon people to God should also be gentle and lenient in his personal attitude.
The importance of this verse is that one should be lenient as an individual, but not in principles.
The Holy Prophet (saw) was very firm when it came to principles and showed no flexibility or softness. If some one insulted him, he would forgive them kindly, because that was something related to himself. But if anyone violated Islamic laws and rulings, the Holy Prophet would treat them with severity and justice.
Once someone stopped the Holy Prophet (saw) and claimed that the prophet owed him some money and that he would not let him go unless he received the amount immediately. The Holy Prophet said: "I don't owe anything, but even if I do, let me go home to get you your money". The man said that he would not let the Prophet take another step. Ignoring how gently the Prophet (saw) had behaved, the man acted fiercely and rudely, to the point that he took the Holy Prophets gown off and wrapped it around his neck and pulled it, until it became bruised.
The Holy Prophet (saw) had been on his way to the Mosque and when people noticed that he was late, they went in search of him and found a Jew obstructing in the way. At that point the Muslims wanted to slap and punish this rude fellow, but the Holy Prophet (saw) said: "No, you people don't interfere, I know what to do with my friend". Observing this humble attitude and leniency, the Jew embraced Islam right there and said: "You are so powerful yet you are so lenient, and this is not possible for an ordinary man. I bear witness there is no God except Allah and that you Mohammad are the messenger of Allah."
When the Holy Prophet (saw) entered Mecca after the city had been conquered, a woman from amongst the wealthy Quraish aristocrats had stolen something important and and according to Islamic rules, her hand had to be cut off. The women was a popular influential figure of Quraish, and her relatives tried to save her by persuading the Prophet not to go ahead with the ruling because the women was the daughter of such a wealthy and upperclass family and if her hand was to be cut off the whole family would be disgraced.
The Prophet said: "Impossible, I cannot suspend the ruling. If this women was not a member of the aristocracy (rich & famous) you would all agree that she must be punished, but now you say she should not be punished because she would be disgraced. How can I forgive her? Never. The laws of Allah will never be suspended and no excuses will be accepted".
From the two incidents we see that the Holy Prophet (saw) never compromised in matters regarding principles, but when his own interests were in question, he was extremely lenient and generous. Some of the reasons behind the progress of Islam were because of his excellent conduct, attitude and characteristics displayed by the Prophet (saw) and the way he lived.
His great role as a Prophet, Messenger, guide, leader and all the great characteristics of different personalities combined into one man excelled him over all other men in history, and also because of the Holy Quran, which was a miracle given to the Holy Prophet (saw) from Allah. The unique beauty, depth, elegance and attraction of the Holy Quran left a great impact in the spread of Islam.
This is why Allah mentions in the Holy Quran in regards to the greatness of the Holy Prophet.
"And surely you are of an exalted character". (Quran 68:4)
Thus a man who talks or preaches from his heart, will win the hearts of others, and whoever talks and preaches from his mouth, his words will not penetrate hearts. In the messages delivered by men of God, this point is clearly observed but not in the messages of other leaders of the world.
The Holy Prophet Mohammad (saw) transformed the world from it's ignorance and idol worship to that of monotheism and salvation. He carried out the most remarkable tasks under unbelievable hardships but always maintained his kindness, generosity and forgiveness, which truly characterises the messenger of God. In him the highest perfections were assembled. He was in reality that perfect infallible man before whom the angels were ordered to prostrate. That is why Allah and his angels praise and bless him and those who are faithful are commanded to also praise and bless him and are required to learn, follow and benefit from the life and teachings of the Prophet Mohammad.

By Martyr Murtaza Mutahari

Reference: ImamReza.net