Musannaf Ibn Abi Shaybah

Hazrat Hasan bin Salih says that I asked Hazrat Ja'd bin Zikwan whether he was present with Hazrat Shurayh when he said that he enforces the testimony of a witness? He replied, yes, provided that he is just.

Hazrat Shurayh used to enforce the testimony upon the witness when testimony was given before him.

Hazrat Shurayh did not consider the testimony of another person against a witness to be permissible as long as that witness was alive, even if he was in Yemen.

Hazrat Sha'bi says that the testimony of a witness is not accepted unless they are two.