Musannaf Ibn Abi Shayba 3:4307

Muhammad ibn Fudayl narrated to us, from Husayn, from al-Qasim ibn Abi Ayyub, who said: I used to be with Sa’id ibn Jubayr, and I would pray four rak’ahs after the Isha prayer. Then I would speak to him, but he would not speak to me until he slept.