The propagation through practice of Islam by the Holy Prophet and the increase in the number of his followers paved the way for the open invitation of the people to Islam. God commanded the Holy Prophet of Islam to invite his close relatives. 'And warn your nearest relatives' (26:214).
In this way, backbiters could not say, Why do you not call your own relatives to worship the One God and warn them of God's severe punishment?' Moreover, the support of the relatives of the Prophet would help the promotion of Islam. So the Holy Prophet told Ali to prepare a meal and invite their relatives, who numbered about 40. After preparing the meal, Ali invited them. All the relatives of the Holy Prophet accepted the invitation and ate the meal prepared by the blessed hands of Ali.
Although the food was not sufficient for even one person, all 40 people were full after eating that blessed food and, strangely enough, the food had not diminished at all. This amazed all of them but the obstinate Abu Lahab, who said without thinking, "This is magic and charms". The foolish man disregarded the fact that magic and charms cannot feed people!
On that day the Prophet said nothing about the matter. Perhaps his silence was due to the fact that he wanted them to realize the difference between a miracle' and magic' because if magic were the cause the guests would feel hungry after leaving the house of the Holy Prophet.
Since this gathering did not give any favourable result, the Holy Prophet invited them for the next day. Again the same reception was repeated and all were filled. Yet the food was not reduced even after the meal was over.
Then the Prophet said, O sons of Abdul Muttalib. God has assigned me to warn you of the painful torments of the wrongdoers and give you the good news of His reward to the pious believers. Become Muslims and follow me to achieve salvation. I swear by Almighty God that among all Arabs I do not know anyone who has brought his people anything better than what I have brought you. I have brought you prosperity and salvation both in this world and in the hereafter. The Gracious God has commanded me to call you all to worship Him. Now which one of you is willing to help me with the task? Anybody who announces his readiness to help me will be my brother, my successor, and the executor of my will'.
Nobody answered but Ali, who was the youngest. He stood up and said, "O Prophet of God. I am your assistant. I am your supporter".
The Prophet asked him to sit down. He repeated the same saying three times but no one except Ali replied to him. Then the Prophet pointed to Ali and said: "He is my brother, my successor and the executor of my will among you. Listen to him and obey him"1
It was on this very day that a number of people came to believe in the faith of the Holy Prophet of Islam, but ignorance and bigotry hindered some of his relatives from believing in his message. However, this gathering was effective in gaining support for the Holy Prophet.
In addition to the fact of the extraordinary event - 40 people being fed with a small amount of food - there is another remarkable point in this event - the remarks the Holy Prophet made about his cousin Ali on that day. They clearly prove the fact that Ali was the Prophet's righteous successor and Caliph, and thus we must regard Ali as the successor of the Holy Prophet of Islam.
Thus the way was paved for the public invitation of the people to Islam and open propagation of this divine faith. The Prophet demonstrated indefatigable perseverance in fulfilling this divine duty and did not stop his invaluable teachings, outreach and struggles for a single hour. It was then that the magnificent banner of Islam was hoisted and truth began to be promoted.
* A Glance at the life of the Holy Prophet of Islam, by Dar Rah Haqq Board of Writers.
1- Tarikh Tabari, Vol. 3 p. 1171-1173; Tafsir Majma' al-Bayan, Vol 7, p. 206; Bihar al-Anwar, Vol. 18 p. 192. This point is confirmed by all Islamic as well as non-Islamic historians and is among the confirmed facts of History. Al-Ghadir, Vol. 2, p. 278.