In what situations is the supplication for expiation of the assembly (Kaffarat al-Majlis) recited?

The supplication for expiation of a gathering (Du'a Kaffarat al-Majlis) is prescribed for a Muslim at the end of their gathering or conversation, to serve as an expiation for any idle talk that may have occurred. It has been reported that the Prophet, peace and blessings be upon him, used to say, when he wished to rise from a gathering: "Glorified are You, O Allah, and praised are You. I bear witness that there is no god but You. I seek Your forgiveness and repent to You."

As for finishing ablution (wudu'), it is prescribed to recite the supplication reported from the Prophet, peace and blessings be upon him: "I bear witness that there is no god but Allah alone, without partner, and I bear witness that Muhammad is His servant and His messenger." It was also reported: "O Allah, make me among those who repent and make me among those who purify themselves."