Jami` at-Tirmidhi 461
جامع الترمذي#461Sahihحَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ أَنَسِ بْنِ سِيرِينَ، قَالَ سَأَلْتُ ابْنَ عُمَرَ فَقُلْتُ أُطِيلُ فِي رَكْعَتَىِ الْفَجْرِ فَقَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم يُصَلِّي مِنَ اللَّيْلِ مَثْنَى مَثْنَى وَيُوتِرُ بِرَكْعَةٍ وَكَانَ يُصَلِّي الرَّكْعَتَيْنِ وَالأَذَانُ فِي أُذُنِهِ . يَعَنِي يُخَفِّفُ . قَالَ وَفِي الْبَابِ عَنْ عَائِشَةَ وَجَابِرٍ وَالْفَضْلِ بْنِ عَبَّاسٍ وَأَبِي أَيُّوبَ وَابْنِ عَبَّاسٍ . قَالَ أَبُو عِيسَى حَدِيثُ ابْنِ عُمَرَ حَدِيثٌ حَسَنٌ صَحِيحٌ . وَالْعَمَلُ عَلَى هَذَا عِنْدَ بَعْضِ أَهْلِ الْعِلْمِ مِنْ أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم وَالتَّابِعِينَ رَأَوْا أَنْ يَفْصِلَ الرَّجُلُ بَيْنَ الرَّكْعَتَيْنِ وَالثَّالِثَةِ يُوتِرُ بِرَكْعَةٍ . وَبِهِ يَقُولُ مَالِكٌ وَالشَّافِعِيُّ وَأَحْمَدُ وَإِسْحَاقُ .
Anas bin Sirin narrated that :he asked Ibn Umar about the length of the two Rak'ah (before) Al-Fajr. He said: "The Prophet would pray two and two during the night, and he would perform Al-Witr with one Rak'ah. And he would pray two Rak'ah while he was hearing the Adhan [meaning that they were light]
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 3:9