Musannaf Ibn Abi Shayba 3:2748

Katheer bin Hisham narrated to us, from Ja'far bin Burqan, who said: Thabit bin al-Hajjaj narrated to me, from Ibn Umar, who said: We used to perform the Jumu'ah prayer, then we would return and take a midday nap (qaylulah).