E. References to Tekhelet shel tzitzit in the Gaonic Literature

Mar Sar Shalom, Gaon (d. 859) speaks of Tekhelet as of a thing of the past:

ביד ישראל כשהיתה תכלת

Rab Nahshon Gaon (d. 889) in a responsum partly cited in the Ittur gives the Arabic equivalent for Tekhelet, saying nothing further. His silence implies that the inquirers to whom his answer was addressed had only asked for the interpretation of the word, not for information about the existence of the thing, its non-existence in the ritual being universally known.

In the Code of R. Simon Kahira written about 900 the non-existence of Tekhelet shel tzitzit is implied though not expressed.¹​

Rab Sherira one of the last representatives of the Gaonic school (930-1000) in his account of the ceremony of the induction of the exilarch (ריש גלותא) makes mention of the use of Tekhelet, Argaman and tola’at shani for decorating the throne-like seat of the Prince of Captivity.

The reference to Tekhelet is no indication of the existence of Tekhelet shel tzitzit in Sherira’s time. Cloth of a colour resembling Tekhelet may have been obtainable but certainly not such as was manufactured by Jews in strict conformity with the requirements of the law for Tekhelet shel tzitzit. But it is highly possible that the term Tekhelet is not meant in its strict sense but is merely used as a colour designation, standing for dark blue (indigo, wood).²

R. Samuel b. Hofni Gaon (d. 1034) in the treatise on tzitzit gives considerable attention to Tekhelet. There is no allusion to the contemporary non-existence or otherwise of Tekhelet shel tzitzit in the two chapters at my disposal, viz. the ninth edited by me and the tenth edited by Dr. Israelsohn.