Hadith 4:786
Hafs narrated to us, from Ibn Jurayj, from Ya'la ibn Umayyah, that he used to say to his companion: "Let us go to the mosque so that we may seclude ourselves (i'tikaf) in it for an hour."
حدثنا حفص عن بن جريج عن يعلى بن أمية أنه كان يقول لصاحبه انطلق بنا إلى المسجد فنعتكف فيه ساعة