The remark of Muhammad about Sa'd bin Mu'adh when he was about to judge the case of Banu Qurayza, "Stand for your chief (Sayyid)," could be taken to justify the view that the Ansar were capable of ruling over Quraysh, and the story was therefore twisted in various ways to remove this implication. (Muhammad at Medina, Oxford, 1966)
The Apostle of God called Sa'd the Chief of the Quraysh. Sa'd was obviously capable of ruling the Quraysh, and why not? After all what was there in the "credentials" of the Quraysh that the Ansar didn't have? Nothing. But the Ansar lost their capability of ruling the Quraysh as soon as Muhammad, their master, died. During the caliphate of Abu Bakr and Umar, it was a "disqualification" to be an Ansari to hold any important position in the government.
Laura Veccia Vaglieri
As he lay dying, Umar was anxious about the succession and he appointed a committee of six, all Qurayshites, whose duty it should be to choose one of their number as caliph. The inhabitants of Medina no longer had any share in the election of the head of the state. (Cambridge History of Islam, Cambridge, 1970)
Far from having a share in the election of the head of the state, not to speak of themselves becoming the head of the state, the inhabitants of Medina, did not have a share in anything. They might have given some "advice" to Abu Bakr and Umar. In Saqifa, Abu Bakr and Umar had told them that they would consult them (the Ansar) in all matters.
Few, if any, would challenge the general interpretation of this poignant fact that the most important and most indispensable single factor in the year 1 of Hijri, namely, the support of the Ansar, had become the most striking non-factor in the year 11 Hijri.
The Cassandra utterances of Hubab ibn al-Mandhir in the bedlam of Saqifa proved only too true. He had expressed the fear that the children of the Ansar would beg for food at the doors of the houses of the Muhajireen, and would not get any. Much worse was to come for them in the times of Yazid bin Muawiya.
The Ansar fought in all the campaigns of Abu Bakr and Umar but only as other ranks and never as generals. The new wealth which came flooding into Medina after the conquest of Persia and the Fertile Crescent, also appears to have bypassed them with the exception of a few, who collaborated with the Saqifa government.
Among the latter were the two spies from the tribe of Aus who had squealed on the Khazraj to Umar and Abu Bakr. Others were Muhammad bin Maslama, Bashir bin Saad, and Zayd bin Thabit. They had shown great zeal in taking the oath of loyalty to Abu Bakr in Saqifa.
Zayd bin Thabit was fanatically devoted to Uthman, and for this reason, he received many gifts and rewards from the treasury. He was the son of poor parents but during the caliphate of Uthman, became one of the richest men in Medina.
Two officers of the public treasury in Medina and in Kufa who had been appointed by Abu Bakr, had thrown the keys of the treasuries in their charge, before Uthman, in protest against the plunder of the public funds by himself and by one of his governors. Uthman gave both keys to Zayd bin Thabit.
Zayd bin Thabit was also the chairman of the committee appointed by Uthman to collect the verses of Qur'an, and to publish them in one volume, as noted before.
Zayd bin Thabit was one of the few Ansaris who shared the bonanza in the times of Umar and Uthman. He was also one of the few Ansaris who did not take part in the campaigns of Ali in Basra, Siffin and Nehrwan. Most of the Ansaris fought on Ali's side against his enemies in these battles.