Musnad Ahmad 26:284

Mu'awiyah ibn 'Amr narrated to us, Za'idah narrated to us, he said: Sulayman said: I heard them mentioning, from Ibrahim ibn Suwayd, from 'Alqamah, from 'Abdullah, he said: The Messenger of Allah, may Allah bless him and grant him peace, said: "Your permission to enter upon me is that you lift the curtain."