Musnad Ahmad 1013:15

'Abd al-Rahman ibn Mahdi narrated to us, Sufyan narrated to us, from Abu Hazim, who said: I heard Sahl ibn Sa'd saying: "Men used to pray with the Prophet, may Allah bless him and grant him peace, having their waist-wrappers tied around their necks like the manner of young boys. So it was said to the women: Do not raise your heads until the men have become level in sitting."