The Messenger of Allah ﷺ prayed Zuhr as five rakahs. He was asked, "Has the prayer been increased?"He replied, "What do you mean?"They said, "You prayed five rakahs."So he performed two prostrations after having given the salam.
حدثنا حفص بن عمر ومسلم بن إبراهيم المعنى قال حفص حدثنا شعبة عن الحكم عن إبراهيم عن علقمة
صلى رسول الله ﷺ الظهر خمسا فقيل له أزيد في الصلاة قال وما ذاك قال صليت خمسا فسجد سجدتين بعد ما سلم
Bukhari narrated it in the chapter on prayer, the section on what has been said regarding the qibla, etc., no. 404, and Muslim narrated it in the chapter on mosques, the section on forgetfulness in prayer and the sujud for it, no. 91/572, from the hadith of Shubah, through this chain.