The Prophet ﷺ prayed Dhuhr as five units. He was asked, "Has something been added to the prayer?" He then performed two prostrations after giving the salam.
حدثنا إسحق بن منصور أخبرنا عبد الرحمن بن مهدي حدثنا شعبة عن الحكم عن إبراهيم عن علقمة
أن النبي ﷺ صلى الظهر خمسا فقيل له أزيد في الصلاة فسجد سجدتين بعد ما سلم
Agreed upon [by Bukhari and Muslim]. Bukhari narrated it in the chapter on "The Forgetfulness [in Prayer]," section "If one prays five [rak'ahs]," hadith no. 1226, and Muslim, no. 91/572, from the hadith of Shubah, with this same chain.