A very good and pure spirit existed in the family of Abu Talib. It looked at the world in a peculiar manner and saw all things connected and united with one another.
This spirit was very strong in the prophet and Ali and a very firm relationship existed between them, because Ali had been brought up by the prophet from his childhood till he grew up to be a youth. When we admit that it is possible that good morals should become firm naturally in a heart and a soul we have also to say that Ali was born with perfect faith in the prophethood of Muhammad and support for him, because the qualities and virtues of the Family of Abu Talib in which the prophet was brought up were transferred to his cousin from his birth.[*]
The personality of Ali developed with the virtues of his family. It was this place where he heard Muhammad speak and the call to Islam also started from here.
Ali was quite young when the prophet attached him with himself and called him his brother.
In his sermon entitled "Qase'a" Ali mentions the attention paid to him by the prophet and says: "Do you know, that due to my relationship and on account of my worth and merit, what were my relations with the prophet.
[*] The correct position is this that Abu Talib and the members of his family or the ways and manners of the time or the environments had no influences on the prophethood of Muhammad or the Imamate of Ali. These things were related with divine inspiration and neither Abu Talib nor the members of this family shared the secrets of prophethood and Imamate
From the very beginning of my life he loved me and I loved him. He took me in his lap when I was a baby and thence I was always with him, he often kept me embraced to his heart, he used to make me sleep next to him; we used to be so close to each other that I felt the warmth of his body and smelled the fragrance of his breath.When I was a baby, he fed me with his hands often chewing hard bits for me. He never found me lying nor weak and wavering. From the time of his babyhood God had appointed the Holy Ghost to be always with him and this archangel was leading him towards exemplary qualities and high moral values and I followed the prophet step by step as a baby camel follows its mother. Daily he used to place before me a fresh standard of efficiency and used to order me to follow it. Every year he used to stay in a grotto of the Hira Mountains for sometime, and nobody used to be with him but I. None could then see or hear him or be near him but I. During those days Islam was the religion of only the prophet and his wife Khadijah, I was the third of the trio (the prophet, Khadijah and Ali himself). Nobody else in this world had accepted Islam I even then used to see the divine light of revelation and prophethood and smell the heavenly fragrance of prophethood. When the prophet received the first revelation Satan lamented loudly. I asked the prophet "Who is lamenting and why". He replied, "It is Satan who had given up hopes of acquiring complete sway over human mind. In this disappointment he is lamenting over the chance lost. Verily, Ali, you also hear whatever is revealed to me and you also see whatever is being shown to me. With this difference that you are not entrusted with prophethood, but you will be my successor, helper and vi zier, and you will always uphold truth and justice".
Childhood is the age when one is fully capable of acquiring good qualities. Ali spent a good deal of his life with the prophet alone. He imitated the prophet's conduct and remained separated from his community which was leading a miserable life and was firmly bound with the chains of hereditary customs.
For years Ali lived in a pure atmosphere by the side of his cousin and was loved very much by him. None of the companions and followers of the prophet could develop such a close relationship with him. Ali opened his eyes on the path which had been opened for him by his cousin.
He learnt how to worship God from Muhammad's prayers. He enjoyed the prophet's love, kindness and brotherhood. His relationship with Muhammad was similar to the one between Muhammad and Abu Talib. When Ali first felt the sentiment of love in his mind he loved Muhammad. When he spoke for the first time he spoke with Muhammad. On the very first occasion when he was required to display manliness and valour he showed readiness to support Muhammad. Muhammad's friends were friendly with him and his enemies also respected his personality. Ali was such a protege and disciple of the prophet that he became his soul and a part of his limbs.
In the early days of the prophetic mission of the prophet some elders amongst Quraysh who hated worship joined him. The slaves and helpless persons came round him in expectation of justice and freedom. And after he was successful and victorious a third group also joined him, because those people had no alternative left. They wanted to benefit from the new situation and most of Bani Umayyah belonged to this group. These different groups embraced Islam on different occasions and although they resembled one another in the matter of obedience to the prophet the degrees of their faith differed. However, as Ali was born and brought up in the lap of prophethood, his faith was natural and innate, and he emerged from the body of his mother with this faith in his heart. His faith had nothing to do with age or the vicissitudes of time. He offered prayers and testified the prophethood of Muhammad at an age when a child cannot even express his thoughts. And he did all this without obtaining any order or advice from anyone. Most of the persons who embraced Islam in the early days of Muhammad's prophethood had worshipped the idols in previous days. However, when Ali prostrated
for the first time it was before the Allah of Muhammad. This was the quality of the faith of the person who was destined to grow up as a supporter and well-wisher of the prophet, to lead the faithful after the prophet, and to save the people from the calamities of time.
source : http://www.maaref-foundation.com