Sahih Bukhari
Sahih Bukhari Volume 001, Book 008, Hadith Number 358.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 08. Prayers (Salat)
Narated By Sahl : The men used to pray with the Prophet with their Izars tied around their necks as boys used to do; therefore the Prophet told the women not to raise their heads till the men sat down straight (while praying).