Mus'ab ibn Umayr was the first of ambassador of Rasul Allah in Madinah. Before Rasul Allah had arrived in Madinah, Mus'ab taught ahl al-Madinah about Islam and they began to enter the Deen.

This enraged Sa'd ibn 'Ubaadah, one of the chieftains of Madinah. He sheathed his sword and set off for the head of Mus'ab ibn 'Umayr. When he confronted Mus'ab he threatened, "Stop this nonsense you speak or you shall find yourself dead!"

Mus'ab replied in the way that should be a lesson for us all. This man before him did not stop at rudeness and ignorance, he wanted to slit his throat.

Mus'ab said, "Shall you not sit and listen for a few moments. If you agree with what I say then take it, and if not, we shall desist from this talk." Sa'd sat down.

Mus'ab spoke about Allah and His messenger until the face of Sa'd ibn Ubaadah's face shone like a full moon and he said, "What should a person do who wishes to enter into this Deen?" After Mus'ab had told him he said, "There is a man, if he accepts this Deen, there shall be no home in Madinah that will not become Muslim. Sa'd ibn Mu'aadh."

When Sa'd ibn Mu'aadh heard what was happening, he was infuriated. He left his home to go and kill this man called Mus'ab ibn Umayr for the dissention he had caused. He entered upon Mus'ab and announced, "You shall desist of this religion you speak of or you shall find yourself dead!"

Mus'ab replied, "Shall you not sit and listen for a few moments. If you agree with what I say then take it, and if not, I shall desist from this talk." Sa'd sat.

Mus'ab spoke about Allah and His messenger until the face of Sa'd ibn Mu'aadh's face shone like a full moon and he said, "What should a person do who wishes to enter into this Deen?"

Look at what a kind word did. Sa'd ibn Mu'aadh went home to his Madinan tribe that night and announced to them all, "Everything of yours is Haram upon me until you all enter into Islam."

That night, every home in Madinah went to bed with Laa ilaaha illa Allah.