Zayd-ibn Arqam: When the Messenger of Allah (S.A.W.) returned from his "Farewell Pilgrimage'" "and stopped at Ghadir Khum, he gave an order to sweep the ground under the trees then he said "Verily Allah is my benefactor and I am the guardian of every believer; he then held 'Ali's hand, raised it and said: "Whoever that I am his guardian, this man is his protector. Oh Allah love whoever loves him and be the enemy of those who are his enemies.

The Messenger of Allah (S.A.W.): Whoever likes to live and die like me and enter the paradise to which I have been promised, should accept 'Ali ibn Abi Talib's guardianship status and those of his immaculate inheritors who shall be guiding the people after me, and are as light in the darkness, as they will never let you go astray.

The Holy Prophet (S.A.W.) addressing Ali (A.S.) said: whoever would be glad to see Almighty Allah purified and secure, and be free from the big horror, should accept the guardianship of you, your two sons, al-Hasan(A.S.) and al-Husayn(A.S.), and 'Ali ibn al-Husayn(A.S.) and Muhammad ibn 'Ali(A.S.) and Jafar ibn Muhammad(A.S.) and Musa ibn Jafar(A.S.) and Ali ibn Musa(A.S.) and Muhammad(A.S.) and 'Ali(A.S.) and al-Hasan(A.S.) and Finally al-Mahdi(A.S.) the last one.

The Holy Prophet (S.A.W.): Love and devotion to me and my Ahl al-Bayt make one immune from the Hell Fire.

The Messenger of Allah (S.A.W.): What is the matter with some people that when they hear about Ibrahim's (A.S.) family, they become happy, but when they hear about Muhammad's (S.A.W.) family they become annoyed?! I swear to the One who has got Muhammad's (S.A.W.) soul in His hand; if on the Resurrection Day a believer who has good actions of seventy Prophets is presented before Allah his good actions will not be accepted if those are devoid of the love of me and my family.

Imam al-Baqir(A.S.): Islam has been based on five foundations: performing daily prayers, giving the Zakat, fasting in the holy month of Ramadan, pilgrimage to Makkah and accepting the love and guardianship of Ahl al-Bayt.

Abu Hamza: Imam al-Baqir (A.S.) told me: Verily only those who know Allah worship Allah truly, but those who do not know Allah, worship Him like the ignorant. I asked him: May I be sacrificed to you! What is the sign of knowing Allah? He replied: Believing in Allah and His Messenger and accepting the love and guardianship of Imam Ali(A.S.) and following him and following the Guided Imams(A.S.) and taking refuge in Allah the Glorious and the High this is understanding of Allah the Glorious and the High.

Muhammad ibn Ali al-Halabi: Imam al-Sadiq (A.S.) concerning the following verse: "O my Lord, forgive me, my parents, and him who enters my abode as a believer" (71:28) said that it means the love and guardianship, whoever accepts the love and guardianship enters the house of the prophets, and what is meant by the verse: "Verily, Allah intends to keep off from you (every kind of) uncleanness O you the people of the house and purify you (with) a thorough purification" (33: 33) is the Holy Imams (A.S.) and their love; whoever embodies the love [of Ahl al-Bayt(A.S.)] has entered into the house of the Holy Prophet(S.A.W.).

Imam al-Hadi (A.S.) in Jami'a Supplication: "And the earth lit up with your light and those who were saved reached this state because of you and strived to reach Allah's approval. Wrath of Allah is upon whoever denies your guardianship".

Source:

Ahl al-Bayt (A.S.) in The Qur'an and Hadith