Lawrence H. Schiffman, Texts and Traditions, Ktav, Hoboken 1998, p.522.

Tannaitic tradition understood the dual-Torah concept to be confirmed by the Bible. This concept shows that the tannaim maintained that both Torahs had been given by God to Israel.

“And thy law to Israel” (Deut. 33-10)- This teaches that two laws were given to Israel, one orally and the other in writing.

Agnitos 54 the general asked Rabban Gamliel, 55 “How many laws were given to Israel?” [Rabban Gamliel] said to him, “Two; one in writing and one orally.”

54. This official cannot be identified.

55. Most probably Gamliel II, who served as patriarch between 96 and 115 C.E.