Musnad Ahmad 33:12

'Abd al-Samad narrated to us, Za'idah narrated to us, 'Abdullah ibn Muhammad ibn 'Aqil narrated to us, from Jabir, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of the men's rows is the first, and the worst of them is the last; and the worst of the women's rows is the first, and the best of them is the last." Then he said: "O assembly of women, when the men prostrate, lower your gaze, so that you do not see the 'awrahs (private parts) of the men due to the tightness of their lower garments."