Continuing to talk about the unique features of Imam Ali (AS), we come to the following items:
- The first male Muslim: All historians agree that after the Prophet of Mercy was given the Divine Mission to guide the people, Ali (AS) was the first man to believe in him and support him at the time he was only 10 years old.
- The Prophet’s steadfast supporter: Because of the unique circumstances of that era, the Prophet invited people to Islam secretly for the primary 3 years. During all this time, Ali and Khadija (the Prophet’s beloved wife) were the Prophet’s only supporters in promoting Islam.
- Hadith of warning: 3 years after the revelation of Allah, the Prophet was ordered to make his mission public. To start, he was ordered by God to hold a gathering and invite his relatives. In this invitation, the holy Prophet [PBUH] asked the people present:
”Who is among you to assist me in my way so to be my brother, successor, and representative among people?”
Only Ali (AS) answered:
”O Prophet of Allah, I will support you during this way”.
The prophet [PBUH] repeated this question three times and heard the same answer from Ali (AS). Then he said to people there:
”O my relatives; Know that Ali (AS) is my brother, successor, and Caliph after me among you” 
- God’s testimony to Ali’s (AS) purity: The Prophet (PBUH) would always emphasize Ali ibn Abi Talib’s (AS) purity and piety. God also certified the infallibility of Ali (AS) in the Verse of al-Tathir.
- Courageous defense of the truth: Ali (AS) was always on the Prophet’s side, defending the defenseless people, during the wars that the enemies of the truth launched against the believers in the One God.
- Facing death to guard the Prophet: One night various polytheists from different tribes conspired to assassinate the Prophet in his bed. Ali (AS) volunteered to sleep in the Prophet’s bed that night. When the terrorists attacked the Prophet’s house to cowardly kill him during his sleep, they saw that Ali ibn Abu Talib (AS), not the Prophet [PBUH] was sleeping in the bed. He endangered his own life so that the Prophet and future of Islam would stay safe.
The truth and Ali: The Prophet stated that “Ali is with the truth and the truth is with Ali”. He said this about no other individual. The Prophet also prayed for him by saying, “Oh God, surround the truth around Ali, whichever way Ali turns”.
Taken from “Hidden from the Eyes of the World: Who Are the Shia and What Do They Say?” by Masoud Basiti & Zahra Moradi
 Usd al-Ghabah fi Ma`rifat al-Sahabah (by Ibn Athir), Volume 5, Page 434 and Bihar al-Anwar, Volume 38, Page 211
 Manaqib aale Abi Talib (by Ibn Shahr Ashub), Volume 1, Page 43
 Tarikh (by Tabari), Volume 2, Page 62-63; al-Kamil fi al-Tarikh (by Ibn Athir), Volume 2, Page 40-41
 “ إِنَّما يُرِيدُ اللَّهُ لِيُذْهِبَ عَنْكُمُ الرِّجْسَ أَهْلَ الْبَيْتِ وَ يُطَهِّرَكُمْ تَطْهِيرا” The Holy Quran, Surah al-Ahzab (33:33)
 Tabaqat Ibn Sa’d. Translated by Mahmoud Mahdavi Damghani [Farsi], Volume 3, Page 16
 The following verse of the Quran was revealed in praise of this action of Ali ibn Abi Talib (AS),
ومِنَ النّاسِ مَنْ یشْری نَفْسَه ابْتِغاءَ مَرضاتِ اللَّه واللَّه رءُوفٌ بِالْعِباد
The Holy Quran, Surah al-Baqarah [2:207]
 Tarikh Dimashq (by ibn Asakir), Volume 42, Page 449