Musannaf Ibn Abi Shaybah

Hazrat Shurayh (may Allah have mercy on him) says: First make a claim, then increase it, and seek much increase in it, and then establish just witnesses upon it. Surely, we have been commanded to judge with justice. And ask them, if they say: "Allah knows best," then Allah is the All-Knowing. And if they, being separate, say that he is doubtful (in doubt), then the testimony of one who is doubtful is not valid. And if they say: "We do not know about him except that he is just and a Muslim," then, insha’Allah, he is as such, and his testimony is valid.