Musnad Abu Ya'la al-Mawsili 109:182

Uqbah narrated to us, Yunus narrated to us, he said: Ibrahim bin Isma'il informed me, from Abu al-Zubayr, from Jabir, he said: The Messenger of Allah (may Allah bless him and grant him peace) forbade that one of us should lie down while placing one of his legs upon the other.