'Abbasbin Sahl As-Sa'di said:
"Abu Humaid, Abu Usaid As-Sa'di, Sahlbin Sa'd, and Muhammad bin Maslamah came together and spoke abouttheprayer of the Messenger of Allah (ﷺ). Abu Humaid said: 'I amthemost knowledgeable of you about the prayer of the Messenger ofAllah(ﷺ). The Messenger of Allah (ﷺ) stood up and said AllahuAkbar,and raised his hands, then he raised them when he said AllahuAkbarfor Ruku', then he stood up and raised his hands, and stoodstraightuntil every bone had returned to its place.'" (ID)
English reference (ID): Vol. 1, Book 5, Hadith 863 (ID)
Arabic reference (ID): Book 5, Hadith 912 (ID)