Hazrat Abu Hurairah (RadiAllahu anhu) narrates from Rasulullah (Sallellahu alaihi wa sallam) that there is a group of angels who patrol the earth and wherever they find any gathering of Zikr they call out to each other and form a circle around this gathering that reaches to the sky.
When this gathering disperses, they return to the sky where they are questioned by Allah Ta’ala, although He is All-knowing: Where have you come from? They reply: We come from a gathering of Your servants who are engaged in Tasbeeh, Takbeer and Tahmeed. Allah Ta’ala asks them: Have they seen Me? The angels reply: No. Allah Ta’ala asks: And what if they had seen Me? They reply: Then they would have engaged even more excessively in Your Ibadah and in Tasbeeh (glorifying of) You. Allah Ta’ala says: What are they asking for? They reply: They ask of You Jannah. Allah Ta’ala then asks: Have they seen Jannah? The angels reply: No. Allah Ta’ala asks: And what if they had seen Jannah? They reply: Then they would have been even more desirous, eager and keen for it. Allah Ta’ala says: What are they seeking refuge from? They reply: They ask refuge from the Fire (of Hell).
Allah Ta’ala asks: Have they seen the Fire? The angels reply: No. Allah Ta’ala asks: And what if they had seen it? They reply: Then they would have tried harder to escape from it and they would have been more fearful of it. Allah Ta’ala says: I make you witness that I have pardoned them. One angel exclaims: A certain person was not from them. He came (coincidentally) for some work. Allah Ta’ala says: They are such a people that even those who sit with them (for other work) will not be deprived –
[Bukhari, Muslim, Baihaqi]