Sahih Bukhari Volume 1, Book 10, Hadith 815

حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، قَالَ أَخْبَرَنَا سُفْيَانُ، عَنْ أَبِي حَازِمٍ، عَنْ سَهْلِ بْنِ سَعْدٍ، قَالَ كَانَ النَّاسُ يُصَلُّونَ مَعَ النَّبِيِّ صلى الله عليه وسلم وَهُمْ عَاقِدُو أُزْرِهِمْ مِنَ الصِّغَرِ عَلَى رِقَابِهِمْ فَقِيلَ لِلنِّسَاءِ لاَ تَرْفَعْنَ رُءُوسَكُنَّ حَتَّى يَسْتَوِيَ الرِّجَالُ جُلُوسًا‏

Narrated By Sahl bin Sa'd : The people used to pray with the Prophet tying their Izars around their necks because of their small sizes and the women were directed that they should not raise their heads from the prostrations till the men had sat straight.