The verse of relationship, from the Qur"an, says:
This verse is a clear command from Allah to His noble Prophet. It is as follows:
It is unanimously agreed upon that the kin mentioned in this verse are Ahlul-Bayt (PBUH). There are many traditions narrated by both Shiite and Sunni Scholars, which not only specify the kin mentioned in this verse, but also state their names. Among the narrations mentioned in this regard by Sunni scholars, are the following:
When this verse was revealed, someone said: "Messenger of Allah, who are the kin whose love is obligatory for us?"
The Prophet (PBUH) replied:
"Ali,Fatima, and her two children."
This narration has been reported by the following Sunni scholars
1. Ibn Hajar in his al-Sawa"iq al-Muhriqah.
2. al-Thalabi.
3. Al-Suyuti in al-Durr al-Manthur.
4. Abu Nu"aym in Hilyat al-"awliya
5. al-Hamawayni al-Shafi"i in Fara"id al-Samtayn
Another narration similar to the one stated above, is reported by Tabari and Ibn Hajar; according to this narration the Messenger of Allah (PBUH) is reported to have said:
"Surely Allah made it incumbent on you to love my kin, and I will ask you about them in the hereafter."
Moreover, the following narrations mentioned on the account of Ahlul-Bayt are a few of the many saying of the Imams (PBUH) in which they recite this verse as proof of the fact that loving them is a religious duty:
A. It is written in al-Sawa"iq al-Muhriqah by Ibn Hajar that Imam Ali (PBUH) said:
He then read:
"Say: `No reward do I ask of you for this except the love of those near of kin, and if any one earns any good, We shall give him an increase of good in respect thereof; for Allah is Oft-Forgiving, most ready to appreciate (service). "(42: 23)
B. It has also been reported in the same book that Imam Hasan (PBUH) gave a speech in which he said:
He -- Glory be to Him, said:
"Say: `No reward do I ask of you for this except the love of those near of kin, and if arty one earns any good, We shall give him an increase of good in respect thereof. For Allah is Oft-Forgiving, most ready to appreciate (service).""(42: 23)
C. The fourth Imam, Imam Ali Ibn Hosein (PBUH) replied to the Syrian who said to him while he was a prisoner of the Umayyads inDamascus:
"Praise be to Allah Who killed you..etc. "
Then he (PBUH) said: "Haven"t you read the verse:
"Say: `No reward do I ask of you for this except the love of those near of kin, and if any-one earns any good, We shall give him an increase of good in respect thereof; For Allah is Oft-Forgiving, most ready to appreciate(service). ""(42: 23)
D.Jabir Ibn Abdullah said:
"A Bedouin came to the Prophet (PBUH) and said: "Mohammad, present Islam to me."
"The Prophet replied: `Bear witness that there is no God but Allah, to whom an associate does not exist; and that Muhammad is the slave and Messenger of Allah. "
The Bedouin said: `Do you require any reward from me (for bringing me to Islam)?"
He (PBUH) answered: `No, save loving the nearest of kin."
The Bedouin then asked: `Mine or yours?"
The Prophet (PBUH) said: `My kin."
The Bedouin said: `Let me pay allegiance to you, and may the curse of Allah be on those who do not love you and your kin."
Thus he (PBUH) said: "Amen.""
This narration has been reported by Al-Kinji in Kefayat At-Talib p.31.
Sheikh Amini (may Allah bless his soul) listed forty-five (45) sources in v.3 of Al-Ghadeer which state that the verse was revealed regarding Ali, Fatima, Hasan and Hosein (PBUT). They are: Imam Ahmad, Ibn al-Mundir, Ibn Abu Hatim, Tabari, Ibn Mardawaih, Tha"labi, Abu Abdullah al-Mula, Abu Sheikh Nisaee, Wahidi, Abu Nu"aym, Bagawi, Bazaz, Ibn Maghazili, Hasakani, Muhib al-Deen, Zamakhshari, Ibn Asaker, Abu al-Faraj, Hamueeni, Nishabouri, Ibn Talhe, Razi, Abu al-Saoud, Abu Hayan, Ibn Abu al-Hadeed, Baidhawi, Nasfi, Haithami, Ibn Sabagh, Ganji, Manawi, Qastalani, Zarandi, Khazin, Zargani, Ibn Hajar, Samhoudi, Suyuti, Safuri, Saban, Shab Lanje, Handhrami, and Nabhawi.
source : tebyan