Musnad Abu Ya'la al-Mawsili 109:139

Ishaq and al-Qawariri narrated to us, they said: Bishr bin al-Mufaddal narrated to us, he said: Umar bin Abdullah, the freed slave of Ghafrah, narrated to us, he said: I heard Ayyub bin Khalid bin Safwan mentioning from Jabir, who said: The Messenger of Allah, may Allah bless him and grant him peace, came out to us and said: "O people, indeed Allah has detachments of angels that descend and stand at the gatherings of remembrance on the earth, so graze in the gardens of Paradise." They said: "And what are the gardens of Paradise, O Messenger of Allah?" He said: "The gatherings of remembrance. So go out early and go out late in the remembrance of Allah, and remember Him within yourselves. Whoever wishes to know his status with Allah, then indeed Allah places the servant from Himself where he places Him from himself."