During the first three years of his mission, the Prophet Muhammad (SA) did not propagate Islam openly. In every nook and corner, in the hills surrounding Makkah, he would speak to the people about Islam.
Wherever he found a worthy, rational person, he spoke to him about his Prophethood, and condemned the practices of idolatry and oppression. He would call to mind the injustices of the tyrants, and call for sympathy towards the miserable conditions of the weak. He said to the people:
"I am the last of Allah's prophets. I am commanded by Allah to guide you and to deliver you to the freedom and greatness of worshipping the one True God.
Help me on the path to this wonderful goal."
As a result of Muhammad's (SA) continuous efforts a number of people accepted Islam during these three years, and secretly became Muslims. Then the Prophet received Allah's command: "Call your near relatives to Islam".
Therefore Muhammad (SA) invited about forty of his closest relatives to his home, and when they arrived he greeted them warmly. After the food Muhammad (SA) began to speak but one of the guests stopped him. This man was Abu Lahab the Prophet's uncle.
who said: "Be careful not to let Muhammad trick you", and, as soon as he had said this, he stood up from his place, and the others did the same. Arriving outside the house, the guests said to one another: "Did you see how he fed us all? It was amazing.
There was only a little food there, and yet we are all full. And what a delicious food it was!"
One of them asked: "How could it be that with such a small amount of food we are all full'?"
One of them was angry with Abu Lahab, and said:
"Why did you break up the gathering? We should have listened to what Muhammad (SA) had to say. Why did you stand up and leave the house so soon.
Following this Muhammad (SA) decided to invite them all again. He said to 'Ali (AS): "That day I was not able to tell them about Islam. Prepare another meal and invite them again, maybe I will be able to speak to them this time and lead them to freedom and prosperity."
The day of the invitation came and the guests arrived.
Just as before Muhammad (SA) greeted them warmly and treated them all with respect. After the meal, Muhammad (SA) insisted that his guests remain seated, and listen to what he had to say. Some of them sat quietly, but some like Abu Lahab, began to create a commotion.
The Prophet (SA) told them: "Listen, listen to me.
By Allah, it is for your own good. I am the last of Allah's prophets and I have brought a Divine message for you and for all of mankind, a message of freedom and prosperity. O kinsmen, in the Hereafter you will receive a reward for good deeds and a punishment for your bad deeds. The righteous will receive the beauties of Paradise, and the wrongdoers will receive the sufferings of Hell. O kinsmen, I bring you all the good of this world and all the good of the Hereafter. No one has brought you anything better than this., "Which of you is willing to help me in this work, and be my brother, my minister and my successor?'
At this, the guests were silent. No one replied to this heavenly invitation. Only Ali (AS), who was about 14 years of age, stood up and said: "O Prophet of Allah, I am ready to assist you. I am ready to help you."
Muhammad (SA) looked lovingly at Ali (AS), then he repeated his words and made his request again. Just as before all were silent, until the silence was broken once more by Ali (AS), who said in a firm voice!
O Prophet of Allah, I am ready to assist you. I am ready to help you.
The Prophet (SA) was silent as he cast a meaningful look at the selfless youth's radiant face. Then he spoke again: "O my kinsmen. I have brought you the good of both the worlds. I have been ordered to call you to the worship of Allah to Tawhid (monotheism).
Who is ready to assist me in this: to be my brother, my minister, my executor and my successor?"
Again they were all silent and only 'Ali stood up, this time he spoke in an even firmer voice: "O prophet of Allah, I am ready to assist you. I will help you in everything you wish."
Then, to the amazement of all the guests the Prophet (SA) took Ali's (AS) hand and accepted his promise of support. Then he turned to the guests and told them: "This youth is my brother, minister, executor and my successor. Listen to him and obey him."
This angered all but a few of the guests. They stood up laughing and said to Abu Talib, the head of the tribe; "From today 'Ali has become your ruler!
Muhammad has instructed you to listen to the words of your son and to obey him!"
source : http://www.maaref-foundation.com