Musannaf Ibn Abi Shayba 3:5745

Waki’ narrated to us, he said: Sufyan narrated to us, from Mansur, from Abu Wa’il, who said: I went out with Masruq to al-Silsilah, and he shortened the prayer. He stayed there for years shortening the prayer, and he shortened it when he returned until he entered [the city].