Musannaf Ibn Abi Shayba 13:2412

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: ‘Imran bin Hudayr narrated to us, he said: I said to Abu Mijlaz, "I am called to bear witness, and I dislike it." He said, "Leave what you dislike, but if you have witnessed [something] and are called [to testify], then answer."