When the Messenger of Allah ﷺ sat for the first two rak'ahs, it was as though he was sitting on hot stones.Shuba said, then Saad moved his lips with something, so I said, "Until he stands up?"He replied, "Until he stands up."
حدثنا محمود بن غيلان حدثنا أبو داود هو الطيالسي حدثنا شعبة أخبرنا سعد بن إبراهيم قال سمعت
كان رسول الله ﷺ إذا جلس في الركعتين الأوليين كأنه على الرضف قال شعبة ثم حرك سعد شفتيه بشيء فأقول حتى يقوم فيقول حتى يقوم
[Its chain of transmission is daif]. Abu Dawud Sijistani also narrated it in the Book of Prayer, chapter on shortening the sitting, hadith no. 995, from the hadith of Shubah with the same wording, and it is also found in Musnad Abu Dawud Tayalisi, hadith no. 331. Its defect is apparent, and Tirmidhi, may Allah have mercy on him, explained it.