Musannaf Ibn Abi Shayba 3:3019

Abu Bakr narrated to us, he said: Abu Usama narrated to us, from Musa ibn Muslim, he said: I witnessed Ibrahim al-Taymi, Ibrahim al-Nakha'i, Zirr, and Salama ibn Kuhayl. Zirr and al-Taymi mentioned that on a Friday, they prayed the Friday prayer as four [rak'ahs] in their place, and they were fearful.