Is the Atonement for the Session (Kaffarat al-Majlis) recited only after the obligatory prayers, or after any prayer, and are the proofs for that sound?

It is legislated to recite the supplication of expiation for the gathering (Kaffarat al-Majlis) after completing the obligatory prayers and other acts, and after every gathering or act performed by the servant. It was reported from Aisha (may Allah be pleased with her) that the Messenger of Allah (peace and blessings of Allah be upon him) used to conclude his gatherings, recitations, and prayers with: "Glory be to You, and praise be to You. There is no god but You. I seek Your forgiveness and repent to You." He clarified that whoever spoke good, it would be sealed for him with a stamp, and whoever spoke ill, these words would be an expiation for him. It was also reported from Abu Sa'id Al-Khudri (may Allah be pleased with him) that whoever performs ablution and then recites the same remembrance after his ablution, it will be sealed with a seal and placed beneath the Throne. And it is authentically reported from Jubayr ibn Mut'im (may Allah be pleased with him) that whoever recites this remembrance in a gathering of remembrance, it will be like a stamp upon it, and whoever recites it in a gathering of idle talk, it will be an expiation for him.