مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3271
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that ‘Ikrimah said: I prayed behind an old man in al-Abtah. He said takheer twenty-two times. I went to Ibn ‘Abbas (رضي الله عنه) and mentioned that to him, and he said: May you be bereft of your mother, that is the prayer of Abul-Qasim (ﷺ).
Musnad Ahmad 3294lts isnad is saheeh]