From Sahih Bukhari (Hadith 714):
Narrated Abu Huraira:Once Allah's Messenger (ﷺ) prayed two rak`at (instead of four) and finished his prayer. Dhul-Yadain asked him whether the prayer had been reduced or whether he had forgotten. Allah's Messenger (ﷺ) asked the people whether Dhul-Yadain was telling the truth. The people replied in the affirmative. Then Allah's Apostle stood up, offered the remaining two rak`at and then finished his prayer with Taslim and then said, "Allahu Akbar." He followed it with two prostrations like ordinary prostrations or a bit longer
Reference: Bukhari 714