It wasnarrated from 'Abdullah bin Sarjis that the Messenger of Allah(ﷺ) saw a man performing the two Rak'ah before the morning prayerwhile he himself was performing prayer. When he had finished prayinghe said to him:
"Which of your two prayers did you intend to becounted (i.e., accepted)?"
English reference: Vol. 1, Book 5, Hadith 1152
Arabic reference: Book 5, Hadith 1207