Musannaf Ibn Abi Shayba 33:491

'Abbad ibn al-'Awwam narrated to us, from Husayn, from Mujahid, from 'Abdullah ibn 'Amr, who said: There is no group that gathers and remembers Allah, except that Allah remembers them in a group more honorable and more noble than their group. And there is no group that disperses without having remembered Allah, except that their gathering will be a source of regret for them on the Day of Resurrection.