By brother TripolySunni.
Sahih hadith by Abu Sa’eed al Khudri (RA) that Ali (RA) gave baya’ah immediatly to Abu Bakr al Siddiq (RA):
Abu Sa’eed al Khudri may Allah be pleased with him said: When the Prophet’s (sallalahu alaihi wa ala alihi wa sallam) soul passed away, people gathered at the place of Sa’ad bin Ubadah and amongst them were Abu Bakr and Umar. A Khatib from the Ansar (supporters) spoke: “You know that the Prophet of Allah (sallalahu alaihi wa ala alihi wa sallam) was from the Mouhajirun (immigrants) and his caliph must also be from the Mouhajirun, we were the ansar of the Prophet (sallalahu alaihi wa ala alihi wa sallam) and we will be the ansar of his caliph just as we were his Ansar”. Then Umar bin al Khattab stood up and said “This man from amongst the ansar speaks truth and if it were anything other than this then we would not give you a baya’ah (Pledge of allegiance)”, then he grabbed the hand of Abu Bakr and said: “This is your close companion so give him baya’ah”. Then Umar and the Mouhajirun and the ansar all gave him baya’ah. Abu Bakr stood on the pulpit and he looked at the faces of all the people there but he didn’t seen al Zubair, so he called for him and and he came. Abu Bakr told him: “O son of the Prophet’s (sallalahu alaihi wa ala alihi wa sallam) aunt and his disciple would you want to split the cause of the Muslims?” Zubair said: “Not at all O caliph of the prophet of Allah” then he stood and gave him baya’ah. Then he looked at the faces of the people but did not spot Ali so he called for Ali bin abi Talib and he came. Abu Bakr said: “O cousin of the prophet of Allah and the husband of his daughter would you want to split the cause of the Muslims?” So Ali replied: “Not at all O caliph of the prophet of Allah”, then he stood and gave him baya’ah.
-Mujama’a al Zawa’ed (5/183), rijal are people of saheeh.
-Al Bidayah wal Nihayah (5/281), chain thabit and saheeh.
-Al Mustadrak (3/76) and al Sunan al Kubrah (8/143) with two SAHIH chains
Imam Muslim bin al Hajjaj (Author of Sahih muslim) and Imam al hafiz Muhammad bin Ishaq bin Khuzaymah (Author of Sahih Ibn Khuzaymah) and Imam Ibn Katheer all talked about the importance of this sahih narration.
Here weak narration which agrees with saheeh from above:
In the hadith of Habib bin Abu Thabit: Ali bin Abu talib was in his house then a man came to him and told him “Abu Bakr has gotten ready for the Baya’ah” So Ali went out to the mosque wearing only his Qamis without a Izar or a Ridaa and he was hasty because he hated to be late for the baya’ah, then he gave the Baya’ah to Abu Bakr and sat down and later asked for his Ridaa so it was brought for him and he wore it on top of his Qamis.
Source: Tareekh al tabari 3/207, the chain is broken, it contains Seif bin Umar and he is weak and it contains Abdul Aziz bin Siyah who is trustworthy but is a Shia.
Ali and al Zubair were asked about the baya’ah and they said:
“We were only angry because we were late for the consultation, we see Abu Bakr as the most deserving of the people to this position after the Apostle of Allah (sallalahu alaihi wa ala alihi wa sallam), he is the companion in the cave and the second of the two and we know of his honour and rank, The prophet (sallalahu alaihi wa ala alihi wa sallam) had ordered him to lead the people in prayer while he was alive”.
Sources: Al Bidayah wal nihayah (6/341), Khilafat Abu Bakr p67, chain is good.
Imam Abdullah ibn Ahmad narrated in his “Sunnan” (2/563) via trustworthy narrators:
Narrated Qays bin al Abdi: I Witnesses the sermon of Ali on the day of Basarah, he said: ” He praised Allah and thanked him and he mentioned the Prophet (sallalahu alaihi wa ala alihi wa sallam) and his sacrifice to the people, then Allah swt took his soul. (After he said that) then the Muslims saw that they should give the Caliphate to Abu Bakr (RA) so they pledged their allegiance and made their promise of loyalty, and I gave my pledge and I promised him my loyalty, They were pleased and so was I. He (Abu Bakr) did good deeds and made Jihad until Allah took his soul may Allah have mercy on him.”