Musannaf Ibn Abi Shayba 3:1483

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from ‘Ali ibn Zayd, from Abu Nadrah, from ‘Imran ibn Husayn, who said: I stayed with the Prophet, may Allah bless him and grant him peace, during the year of the Conquest in Makkah. He stayed for eighteen nights, not praying except two rak'ahs. Then he would say to the people of the city: "Pray four, for we are a traveling people."