I asked Ibn ʿUmar, "What is your opinion about the two rakʿat before the Fajr (compulsory) prayer, as to prolonging the recitation in them?" He said, "The Prophet ﷺ used to pray at night two rakʿat followed by two and so on, and end the prayer by one rakʿah witr. He used to offer two rakʿat before the Fajr prayer immediately after the Adhan." (Hammad, the sub-narrator said, "That meant (that he prayed) quickly.)"  

قُلْتُ لاِبْنِ عُمَرَ أَرَأَيْتَ الرَّكْعَتَيْنِ قَبْلَ صَلاَةِ الْغَدَاةِ أُطِيلُ فِيهِمَا الْقِرَاءَةَ فَقَالَ كَانَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ مَثْنَى مَثْنَى وَيُوتِرُ بِرَكْعَةٍ وَيُصَلِّي الرَّكْعَتَيْنِ قَبْلَ صَلاَةِ الْغَدَاةِ وَكَأَنَّ الأَذَانَ بِأُذُنَيْهِ قَالَ حَمَّادٌ أَىْ سُرْعَةً  

Messenger of Allah ﷺ offered witr prayer at different nights at various hours extending (from the ʿIsha' prayer) up to the last hour of the night.  

كُلَّ اللَّيْلِ أَوْتَرَ رَسُولُ اللَّهِ ﷺ وَانْتَهَى وِتْرُهُ إِلَى السَّحَرِ