Sahih al-Bukhari 995Book 14, Hadith 6
حَدَّثَنَا أَبُو النُّعْمَانِ، قَالَ حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، قَالَ حَدَّثَنَا أَنَسُ بْنُ سِيرِينَ، قَالَ قُلْتُ لاِبْنِ عُمَرَ أَرَأَيْتَ الرَّكْعَتَيْنِ قَبْلَ صَلاَةِ الْغَدَاةِ أُطِيلُ فِيهِمَا الْقِرَاءَةَ فَقَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم يُصَلِّي مِنَ اللَّيْلِ مَثْنَى مَثْنَى، وَيُوتِرُ بِرَكْعَةٍ وَيُصَلِّي الرَّكْعَتَيْنِ قَبْلَ صَلاَةِ الْغَدَاةِ وَكَأَنَّ الأَذَانَ بِأُذُنَيْهِ. قَالَ حَمَّادٌ أَىْ سُرْعَةً.
I asked Ibn `Umar, "What is your opinion about the two rak`at before the Fajr (compulsory) prayer, as to prolonging the recitation in them?" He said, "The Prophet (ﷺ) used to pray at night two rak`at followed by two and so on, and end the prayer by one rak`ah witr. He used to offer two rak`at before the Fajr prayer immediately after the Adhan." (Hammad, the sub-narrator said, "That meant (that he prayed) quickly.)"