it was recorded by Abū Yaʿlá in "Musnad" (284/2) where Kāmil ibn Ṭalḥah narrated to us, Ḥammād ibn Salamah narrated from Muḥammad ibn ʿAmr, from Abū Salamah, from Abū Hurayrah in a marfūʿ form. I said: This isnād is good; all its men are trustworthy and well-known from the "Tahdhīb," and the comments on Kāmil and Ibn ʿAmr do not harm [its authenticity]. The ḥadīth is an explicit text that the sunnah is to say the takbīr and then prostrate, and that he would say the takbīr while sitting and then rise. It invalidates what some followers do by extending the takbīr from sitting to standing!