Musannaf Ibn Abi Shayba 33:1307

Abu Usama narrated to us, from Musa ibn Ubaydah, from his brother Abdullah ibn Ubaydah, who said: Safiyyah, the wife of the Prophet, may Allah bless him and grant him peace, saw a group of people who recited a prostration verse and then prostrated. She called out to them: "This is the prostration and the supplication, so where is the weeping?"