Musannaf Ibn Abi Shaybah 18432 — Those who disliked a woman sleeping

Hamidah, the freed slave woman of Umar bin Abd al-Aziz, said: Umar bin Abd al-Aziz (may Allah have mercy on him) used to say: Do not let my daughters sleep lying flat on their backs, for as long as they remain in that state, Satan keeps setting his desire on them.