Musannaf Ibn Abi Shayba 13:3023

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Mis’ar narrated to us, from ‘Abd al-Rahman, who said: Shurayh used to say to the two witnesses: "I did not summon you, nor am I preventing you if you wish to stand up. It is only that you two are the ones who decide [the outcome of the case], and I am protecting myself through you, so protect yourselves."