Musannaf Ibn Abi Shayba 3:3110

Humaid ibn Abd al-Rahman narrated to us, from Hasan, from Ibrahim ibn al-Muhajir, who said: Al-Hajjaj used to delay the Friday prayer. So I, Ibrahim, and Sa’id ibn Jubayr would pray the Dhuhr prayer, then we would talk while he was delivering the sermon. Then we would pray [the Friday prayer] with them, and we would consider it [the prayer with them] a supererogatory (nafilah) prayer.