Are gatherings of dhikr (halaqah) in the Sunnah?

It is a common practice to hold gatherings where dhikr is performed, the assemblies of dhikr known as Halqah. The sanctity of these gatherings can be verified by the hadith narrated by Abu Huraira may Allah be pleased with him, who reported Allah's Apostle ﷺ as saying:

"Truly Allah has angels going about the ways, looking for people of Dhikr, and when they find a group invoking Allah, they call to one another, 'Come to what you have been looking for!' And they circle around them with their wings up to the sky of this world. Then Allah asks them although, He knows it all; 'What do My servants say?'

"And, they reply, 'They say, SubhanAllah (Exalted is Allah's perfection beyond any comparison), Allahu Akbar (Allah is ever Greatest), and Alhumdulillah (All praise be to Allah), and they extol Your Glory.'

"Allah says, 'Have they seen Me?'

"And the angels reply, 'No, by Allah, they have not seen You.' And Allah says, 'How would it be, had they seen Me?'

"And the angels say, 'If they had seen You, they would have worshipped You even more, glorified You more, and exalted You even more.'

"Allah says, 'What do they ask of me?'

"The Angels say, 'They ask you Paradise.' Allah says, 'Have they seen My Paradise?'

"They say, 'No, Our Lord! They have not seen it.'

"Allah says, 'How would it be if they had seen My Paradise?'

"And the angels say, 'If they had seen it, they would have been more avid for it, sought it more, and been more desirous of it.'

"Then, Allah asks them, 'From what do they seek refuge?' And they answer, 'From Hell.'

"Allah asks them, 'Have they seen it?' And the angels reply, 'No, by Allah, they have not seen it.'

"And Allah says, 'How would it be if they had seen it?' And the angels say, 'If they had seen it, they would have fled from it even more, and been more afraid of it.'

"Allah says, 'I charge all of you to bear witness that I have Forgiven them.'

"Then, one of the angels say, 'Our Lord, there is one amongst them such and such who happened to pass (by the assembly) and sat along with them (who had been participating in that assembly), he only came for something he needed.'

"Allah would say, 'I also Forgive him, as they are companions through whom no one who keeps their company shall meet perdition.'" [Sahih al-Bukhari 6408]

The above hadith endorses the significance of the gatherings of dhikr, primarily the gatherings to invoke Allah.

It is narrated by Abu Sa'id Khudri may Allah be pleased with him that Mu'awiya may Allah be pleased with him came to a circle in the mosque and said, "What makes you sit here?" They replied, "We are gathered here to remember Allah."

He said, "I adjure you by Allah? (To tell me whether you are sitting here for this very purpose)" They said, "By Allah! we are here only for this very purpose."

Thereupon, he said, "I have not demanded you to take an oath, because of any allegation against you and none of my rank in the eye of Allah's Messenger ﷺ as I am the narrator of few Hadith. The fact is that Allah's Messenger ﷺ went out to the circle of his Companions and said, 'What makes you sit?' They replied, 'We are sitting here to remember Allah and praise Him for He guided us to the path of Islam and He conferred favours upon us.'

"Thereupon he adjured by Allah and asked if that was the only purpose for their gathering, they said, 'By Allah! we are sitting here only for this very purpose,' whereupon, Allah's Messenger ﷺ said, 'I am not asking you to take an oath because of any allegation against you but for the fact that Gibrael peace be upon him came to me and informed me that Allah was talking to the angels about your magnificence.'" [Musnad Ahmad 5416]

It happens that when one goes to an assembly of dhikr, special peace and tranquillity settles upon the heart, the phenomenon is explained by the hadith, as Allah's Prophet ﷺ said, "Never will a group of people gather in a house from among the houses of Allah for the recitation of Allah's Book, or to study it among themselves, except that a state of spiritual tranquillity, sakina, will descend upon them, and they are overcome by Divine Mercy, and they are surrounded by angels, and they are mentioned by Allah as being among those closest to Him." [Sunan Abi Dawud 1455]