(2) باب سَاعَاتِ الْوِتْرِ
Narrated Anas bin Seereen:
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.)"
Reference: Sahih al-Bukhari 995
In-book reference: Book 14, Hadith 6
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 16, Hadith 109