ﷺ reported that the Prophet ﷺ led them in the noon prayer. He stood up after the first two units without sitting, and the people stood with him. When he completed the prayer and the people were waiting for him to give the closing salutation, he said the takbir while seated and performed two prostrations before the salutation, then he gave the closing salutation.
ﷺ: أن النبي ﷺ: صلى بهم الظهر، فقام في الركعتين الأوليين لم يجلس، فقام الناس معه، حتى إذا قضى الصلاة وانتظر الناس تسليمه كبر وهو جالس، فسجد سجدتين قبل أن يسلم، ثم سلم.
Bukhari reported it in the Book of Adhan (829) and Muslim in the Book of Mosques (570), both from the hadith of Ibn Shihab, who said, Abdul-Rahman bin Hurmuz Araj, the freed slave of Banu Abdul-Muttalib, narrated to me, once he said, the freed slave of Rabia bin Harith, from Abdullah bin Buhaynah Asadi, and he mentioned the hadith. The wording here is Bukhari's, and he titled the chapter, "Regarding one who does not consider the first tashahhud obligatory, because the Prophet ﷺ stood up after the two rakahs and did not go back."Nasai titled it, "Chapter on omitting the first tashahhud" (1177), and in it, they said "Subhanallah," but he continued on, and when he finished his prayer, he performed two prostrations, then gave the taslim.