Is the supplication of the gathering concluded with Surat al-Asr, and is this mentioned in a Hadith?

The Sunnah indicates the permissibility of the supplication for expiation of the gathering: "Glorified be You, O Allah, and praised be You. I bear witness that there is no god but You. I seek Your forgiveness and repent to You." There is no evidence that this supplication includes Surat Al-Asr.