On the authority of Nass...

On the authority of Nass, therefore, the Imamate is restricted, through all political circumstances, to a definite individual among all the descendants of 'Ali and Fatima, whether he claims the temporal rule for himself or not. Naturally, the transfer of the Imamate through Nass would be both incomplete and meaningless unless it could be traced back to the person of 'Ali, who should have been entrusted with the office of the Imamate by the Prophet himself.

The Nass thus initiated by the Prophet came down from 'Ali to Hasan, from Hasan to Husayn, and then remained strictly in the line of Husayn until through successive Nass it reached Ja'far. This theory, as we shall see presently, distinguished Ja'far's Imamate from all other claimants, who did not claim a Nass from any preceding Imam. Zayd clearly denied that there was an explicit Nass or designation of 'Ali by Muhammad,[^1] or that there was any designation of the next Imam by the preceding one.

Nor did Muhammad an-Nafs az-Zakiya or his brother Ibrahim ever resort to the principle of Nass from any preceding authority. On the contrary, as Ash'ari points out,[^2] the idea of Nass was the key trait of the Rawafid[^3] as opposed to the supporters of Zayd and later on An-Nafs az-Zakiya.

Ash'ari's statement is in accordance with the unanimous reports given by the Twelver writers themselves, such as Nawbakhti; Sa'd al- Ash'ari, and Kashshi, of Muhammad al-Baqir's followers, who upheld him against Zayd as the only legitimist 'Alid authority on the principle of Nass though the doctrine of Nass was not yet fully elaborated in his time.

A comparison between the traditions related from Al-Baqir and those from Ja'far would demonstrate that Ja'far became increasingly clear and emphatic in his expositions on the doctrine of the Nass Imamate.