Ali (A.S.) was only ten when the Prophet (S.A.W) was inspired by the Almighty to declare his office and preach Islam. Ali (A.S.) and Khadija (Prophet (S.A.W)’s wife) were the only two persons who upheld his claim and prayed behind him. Ali (A.S.) often took pride in being the first and the youngest Muslim in the world.

Hardly three years had passed from his first declaration of Prophethood that Allah enjoined upon him to preach Islam to his own kinsmen. Ali (A.S.) was directed to make preparations for a feast and invite the members of Bani Hashim clan. Forty Hashimites participated. After the party the Prophet (S.A.W) rose and said, "O sons of Abdul Mutallib, I know no man in Arabia who brought for his people better tiding than that which I have brought for you. It will serve you in this life and in the life to come. Will you believe me if I tell you that your enemy is going to attack you by day or night? With one voice they replied, "We believe you to be a truthfulman!" The Prophet (S.A.W) then said, "Then know you all that Allah has sent me to guide man to the Right Path, and has commanded me to call my near relatives first to His Holy Will, and to warn them against His wrath. Who amongst you will share my burden, who amongst you will come forward to help me in this great task? Whoever accepts this responsibility will be my successor, my brother, and my delegate." No one answered. The spell of skeptic astonishment was at last broken by the spontaneous courage of Ali (A.S.). He stood and said, "O Prophet of Allah though my legs are thin, I promise that I will help thee. I am prepared to sacrifice everything on thy command. I am the man, whosoever rises against thee, I shall dash out his teeth, tear out his eyes, break his legs and rip up his belly. O Prophet of Allah I will be thy Wazir over them." The Prophet (S.A.W) asked Ali (A.S.) to sit down asked the same question again, and again it was only Ali (A.S.) who answered the call of the Prophet (S.A.W). The Prophet (S.A.W) again asked Ali (A.S.) to sit down and again asked the same question to the gathering and again none spoke except Ali (A.S.) who again offered himself to serve at the command of the Prophet (S.A.W). The Prophet (S.A.W) then declared, "Listen O People of Quraish, here is Ali, who is My Wazir, My Brother and My Successor. Listen to him and obey him." The assembly broke up in laughter at the thought of a lad of twelve deciding on such an enterprise. Some of them cutting jokes with Ali (A.S.)’s father said, "O Abu Talib, now you should listen and obey your own youngest son." [Tabari, Vol. 2,
page 216].

After appointing his successor the Prophet (S.A.W) started preaching Islam openly. He was now speaking against the idols whom the Quraish so dearly loved and worshipped. This angered them and the other Meccans very much and when they failed to stop him they instigated their youngsters to misbehave and harass the Prophet (S.A.W). They teased him, insulted him, and threw stones and dirt on him. Ali (A.S.) became the Prophet (S.A.W)’s defender. He attacked them and hammered them. He fought even with those who were much older to him and often got hurt, but he never shed the responsibility of punishing the harassers of the Prophet (S.A.W). He was so famous for his attacks on the enemies of the Prophet (S.A.W) that people nicknamed him Kasif (the breaker). Nobody could harm the Prophet (S.A.W) when Ali (A.S.) was with him. But as Islam spread, the anger and frustration of the Quraish and the other Meccans also grew, and their harassment became so severe that the lives of the converts became very miserable.

When the Prophet (S.A.W) saw that the Muslims cannot bear these sufferings any more he advised them to migrate to the Christian country of Abisinia (Ethiopia). Some three hundred men, women and children under the leadership of Ali (A.S.)’s brother Jafar migrated. The Quraish angered by this step of the Prophet (S.A.W) sent their messenger to the king Najashi of Ethiopia requesting him to send back these refugees who were all criminals and had wronged them. When Abu Talib (A.S.) heard about this move of the Quraish, he immediately sent a letter to the king, explaining the entire situation and requesting him not to withdraw the support which he had so generously given to the Muslims. The king acting on the advice of Abu Talib (A.S.) refused to oblige the Quraish [Seerat Ibne Hisham, Vol 1., page 356].

During the fifth year after the declaration of his mission a girl was born to the Prophet (S.A.W) who was named Fatema. She was the only surviving child of the Prophet (S.A.W). Before her birth a son was born to the Prophet (S.A.W) from Khadija and was named Qasim but he died in his infancy. Similarly, the Prophet (S.A.W) got another son from his another wife Maria after migrating to Madina. The Prophet (S.A.W) named him Ibrahim but he to died in his infancy.

When the news of Fatema (S.A.)’s birth was given to the Prophet (S.A.) he said, "I inhale her fragrance and her sustenance is with Allah."

Seven long years of torture, sufferings and hardships did not deter the Prophet (S.A.W) from preaching Islam. Ali (A.S.) now seventeen and stronger than before was as close to him as on the day of the declaration of Islam. The Prophet (S.A.W)’s message of one God, one book, one nation and one flag continued to spread among the whole of Arabia and the Quraish began to realized that if not checked now, this religion and this man Mohammad (S.A.W) will certainly bring their doom. Fearing this the elders of the Quraish assembled to decide their future course of action so that the spread of Islam may be checked. This conference and its proceedings is recorded in history which is as follows:

Nobody except the relatives of Khadija helped them and supplied them food grains and water secretly. Abu Bakr and Umar who had embraced Islam by then and were calling themselves the friend of the Prophet (S.A.W) never cared to supply any food to the Prophet (S.A.W) and his family though there was no restriction on them and they were freely moving about.

Though Abu Talib (A.S.) had left Mecca to avoid any confrontation and was living a quiet life in the mountain pass the demand for Mohammad (S.A.W) still continued. But Abu Talib (A.S.) not only refused to hand over his nephew Mohammad (S.A.W) to them but also allowed him to continue his preachings. He and his son Ali (A.S.) were always with Mohammad (S.A.W), wherever he went [Tabari Vol 12 page 215]. Abu Talib (A.S.) was so concerned about the safety of his nephew that he made him sleep on his own bed and shifted him to other beds when Mohammad (S.A.W) fell asleep. Ali (A.S.) was generally made to sleep on the bed the Prophet (S.A.W) vacated. But the Prophet (S.A.W)s zeal for preaching Islam was so great that during the Hajj period he used to come out of the pass to speak about Islam to the pilgrims. During such dangerous moments Ali (A.S.) accompanied him as a brother, as a friend and as a bodyguard. Like a shadow he moved with the Prophet (S.A.W) wherever the Prophet (S.A.W) went.