The opinion of Sunan-o-Abi Dawood al-Sajistani, ‘The Ummah will be unanimous about them’, is weak for the following reasons:
1) It is clear that an action is attributed to its subject only when it is performed with freewill, without any force or compulsion. So, even if we accept that the Messenger of Allah (s.a.w.a.) has said, ‘they will be unanimous’, it only implies the unanimity of the nation with their own freewill. Don’t you think that it is incorrect for anybody to declare that the Islamic Ummah, including the people of Makkah, Madinah, great jurists, renowned traditionalists, companions of the Prophet (s.a.w.a.) and the Taabein, at any given time, was unanimous on the appointment of Yazid as the caliph of the Muslims? But he claims that they were unanimous in this appointment and chose him for caliphate. He also goes on to claim the consensus of the Muslims on the caliphate of Waleed Ibn Yazid.
2) If we rely on this theory, it will necessitate the exclusion of Ameerul Momineen Ali Ibn Abi Taalib (a.s.) and Imam Hasan (a.s.) from the list of the caliphs because of the opposition of the Syrians for these two, and their unstinted support for their enemies.
3) This portion seems to have been interpolated as it is not found in a number of reliable and consecutive traditions available on the subject. Therefore, there exists a strong probability that this part ‘the Islamic Ummah will be unanimous on all of them’ appears to have been added by the narrator, possibly as an explanation for the tradition. Even if we assume that this part did occur in the original tradition and when there is a controversy between the added part and the missing part then, as a rule, the added part is not relied upon. The same applies here because the majority of the traditions do not comprise of the additional part and only Abu Dawood has narrated it.
Hence, it is incorrect and improper to disregard the many traditions, reliable and consecutive, narrated by a group of companions like Abdullah Ibn Masood and Jaabir Ibn Samarah and a number of Taabein just for the sake of one narration.
So, is it wrong to impute such a probability to this statement?
4) Even if we assume that this statement is correct and found in the original, it is limited by the other sentences found in the numerous other traditions like,
- ‘All of them will act with guidance and the true religion’,
- ‘If they do not exist, the earth will be destroyed with all its inhabitants’,
- ‘They are like the companions of Eesaa (a.s.) and the chiefs of the Bani Israel’, and
- ‘Caliphate is confined only to them’.
Thus, assuming that this statement does exist in the original, its only correct interpretation and construction is that the Ummah will be unanimous on the Imamat of the twelve Imams (a.s.) and acknowledge their Caliphate after the reappearance of Hazrat Mahdi (a.t.f.s.).
(Abridged from the English translation of the book ‘Muntakhab al-Asar’, vol. 1, (published by Naba Publications, Tehran, Islamic Republic of Iran) by Ayatollah Lotfollah Saafi Golpaygani (may Allah prolong his life))!
 Tarikh al-Khulafaa, pg. 10.