Musannaf Ibn Abi Shayba 3:5806

Abu Bakr narrated to us, he said: Abd al-Wahhab al-Thaqafi narrated to us, from Ubayd Allah ibn Umar, he said: I was informed regarding al-Qasim and Salim that they used to say: The people of Mecca, when they go out to Mina, they shorten [the prayer]. He said: And Ata and al-Zuhri used to say: They complete [the prayer].