Musannaf Ibn Abi Shayba 16:966

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Ayyub, from Nafi’, from Aslam, who said: When ‘Umar arrived in Ash-Sham, a man from the Dihqans (landed gentry) came to him and said: "I have prepared food for you, and I would like for you to come so that the people of my district may see my honor in your eyes and my status with you," or as he said. He said: So he (Umar) said: "We do not enter these churches," or he said: "these houses of worship that contain images."