172 THE EVIDENCE OF ISNĀDS

Whether this happened to the lower or to the higher part of the isnād or to both, the existence of a significant common link (N.N.) in all or most isnāds of a given tradition would be a strong indication in favour of its having originated in the time of N.N. The same conclusion would have to be drawn when the isnāds of different, but closely connected traditions showed a common link.

The case discussed in the preceding paragraph is not hypothetical but of common occurrence. It was observed, though of course not recognized in its implications, by the Muhammadan scholars themselves, for instance by Tirmidhi in the concluding chapter of his collection of traditions. He calls traditions with N.N. as a common link in their isnāds 'the traditions of N.N.', and they form a great part of the traditions which he calls gharīb, that is transmitted by a single transmitter at any one stage of the isnād.

A typical example of the phenomenon of the common transmitter occurs in Ikh. 294, where a tradition has the following isnāds:

Prophet, Prophet, Prophet

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Jābir, Jābir, Jābir

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a man of the Banū Salama, Muṭṭalib, Muṭṭalib

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'Amr b. Abī 'Amr the freedman of Muṭṭalib

|

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'Abdal'azīz b. Muhammad, Ibrāhim b. Muhammad, Sulaimān b. Bilāl

| | anonymous

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Shāfi'ī, Shāfi'ī, Shāfi'ī

'Amr b. Abī 'Amr is the common link in these isnāds. He would hardly have hesitated between his own patron and an anonymous transmitter for his immediate authority.

The following example will show how the argument drawn from a common transmitter can be used, together with other considerations, in investigating the history of legal doctrines.