From Sahih Muslim (Hadith 1270):
Abdullah b. Buhaina al-Asadi, the ally of Abual-Muttalib, reported:The Messenger of Allah (ﷺ) stood up in the noon prayer (though) he hadith sit (after the two rak'ahs). When he completed the prayer he performed two prostrations and said," Allah is the Most Great" in each prostration, while he was sitting before pronouncing salutation, and the people performed prostration along with him. That was a compensation for he had forgotten to observe jalsa (after two rak'ahs)
Reference: Muslim 1270