مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3632
Musnad of Abdullah bin Mas'ood
It was narrated from Abu 'Ubaidah, from his father, that The Prophet (ﷺ) would, after the two rak'ahs (i.e., in the first tashahhud), be as if he were (sitting on) baked stones. I (the narrator) said: Until he got up? He said: Until he got up.
Musnad Ahmad 3656Its isnad is da'eef because it is interrupted, Abu ‘Ubaidah,