Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.102.
Joining the assemblies or circles of zhikr is a commendable practice as shown by the following hadith: Ibn ‘Umar reported, “The Prophet, peace be upon him, said, ‘When you pass by a garden of Paradise, avail yourselves of it.’ The Companions asked, ‘What are the gardens of Paradise, O Messenger of Allah?’ The Prophet, peace be upon him, replied, ‘The assemblies or circles of zhikr. There are some angels of Allah who go about looking for such assemblies of zhikr, and when they find them they surround them’.”
Muslim reports that Mu’awiyyah said, “The Prophet, peace be upon him, went out to a circle of his Companions and asked, ‘What makes you sit here?’ They said, ‘We are sitting here in order to remember Allah and to praise Him because He guided us to the path of Islam and he conferred favours upon us.’ Thereupon he adjured them by Allah and asked if that was the only purpose of their sitting there. ‘They said, By Allah, we are sitting here for this purpose only.’ At this the Prophet, peace be upon him, said, ‘I am not asking you to take an oath because of any misapprehension against you, but only because Gabriel came to me and informed me that Allah, the Exalted and Glorious, was telling the angels that He is proud of you’.”
Abu Sa’id Al-Khudri and Abu Hurairah reported that the Prophet, peace be upon him, said, “When any group of men remember Allah, angels surround them and mercy covers them, tranquillity descends upon them, and Allah mentions them to those who are with Him.”
Qatadah reported that Anas ibn Malik said, “The Prophet, peace be upon him, said, ‘When a human is laid in his grave and his companions return and he hears their footsteps, two angels will come to him and make him sit and ask him, “What did you say about this man, Muhammad, may peace be upon him?” He will say, “I testify that he is Allah’s servant and His Messenger.” Then it will be said to him, “Look at your place in Hell-Fire. Allah has exchanged for you a place in Paradise instead of it”.’ The Prophet, peace be upon him, added, ‘The dead person will see both his places. As for a non-believer or a hypocrite, he will respond to the angels, “I do not know, but I used to say what the people used to say!” It will be said to him, “Neither did you know nor did you seek guidance from those who had knowledge.” Then he will be hit with an iron hammer between his two ears, and he will cry and that cry will be heard by all except human beings and jinns’.” (Bukhari and Muslim)