Musannaf Ibn Abi Shayba 28:1120

Ibn Numayr narrated to us, he said: Ubayd Allah ibn Umar narrated to us, from Nafi, from Ibn Umar, who said: Umar ibn al-Khattab arrived from the expedition of Sargh. When he reached al-Jurf, he said: "O people, do not approach the women [at night] by surprise, and do not take them by surprise." Then he sent a rider to Medina [to announce] that the people would be entering in the morning.