Musannaf Ibn Abi Shayba 22:389

Waki’ narrated to us, from Sufyan, from Mansur, from Ibrahim, who said: The companions of Abdullah who used to issue legal rulings (fatwas) and recite the Quran were Alqama, Al-Aswad, Ubaydah, Masruq, Amr ibn Sharhabil, and Al-Harith ibn Qays.