The Prophet ﷺ passed by a man who was praying while the dawn prayer had already been called. He said something to him that I could not make out. When the man finished, we gathered around him and asked, "What did the Messenger of Allah ﷺ say to you?"He replied, "He said to me, 'One of you is about to pray Fajr as four units.'"
حدثنا أبو مروان محمد بن عثمان العثماني حدثنا إبراهيم بن سعد عن أبيه عن حفص بن عاصم
مر النبي ﷺ برجل وقد أقيمت صلاة الصبح وهو يصلي فكلمه بشيء لا أدري ما هو فلما انصرف أحطنا به نقول له ماذا قال لك رسول الله ﷺ قال قال لي يوشك أحدكم أن يصلي الفجر أربعا
Bukhari narrated it in the Book of Adhan, chapter "When the prayer has been called, there is no prayer except the prescribed one," hadith no. 663, and Muslim narrated it in the Book of Travelers' Prayer, in the previous chapter, hadith no. 711, from the hadith of Ibrahim, with this chain.