Musnad Ahmad 1167:37

Ibrahim ibn Khalid narrated to us, he said: Rabah narrated to us, from Ma’mar, from al-Zuhri, from some of them, from a freed slave of Asma’, from Asma’, that she said: The Muslims were in need, and they would wrap themselves with this striped garment (namirah). It would only reach the middle of their shins, or something like that. So I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whoever believes in Allah and the Last Day—meaning the women—let her not raise her head until we raise our heads," out of dislike that she should look at the private parts of the men due to the smallness of their lower garments.