Abu Hurairah (May Allah be pleased with him) reported:
Messenger of Allah (ﷺ) said, "Whoever sits in a gathering and indulges in useless talk and before getting up supplicates:
سبحانك اللهم وبحمدك، أشهد أن لا إله إلا أنت، أستغفرك وأتوب إليك
Subhanaka Allahumma wa bihamdika, ash-hadu an la ilaha illa Anta, nastaghfiruka wa natubu (plural) ilaika
O Allah, You are free from every imperfection; praise be to You. I testify that there is no true god except You; I ask Your Pardon and turn to You in repentance
...he will be forgiven for (the sins he may have intentionally or unintentionally committed) in that assembly. [At-Tirmidhi][1]
Reciting Suratul Asr upon departure
Al-Tabarani: when humankind finds itself at a loss; it can revive itself by returning to the formula provided by the third verse and the four principles/conditions, which are adhered to as a foundation. We saw how these four principles operated on both physical and spiritual levels. This is probably the reason why the companions of the Prophet did not want to become heedless of the foundational message of Islam. Consequently, they used to meet one another and only depart until one of them recited surat-Al-Asr to the other and they bid peace upon one another. [2]
See also: Salatul Ibrahimiyya