Muwatta Malik 182

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عَامِرِ بْنِ رَبِيعَةَ، يَقُولُ صَلَّيْنَا وَرَاءَ عُمَرَ بْنِ الْخَطَّابِ الصُّبْحَ فَقَرَأَ فِيهَا بِسُورَةِ يُوسُفَ وَسُورَةِ الْحَجِّ قِرَاءَةً بَطِيئَةً فَقُلْتُ وَاللَّهِ إِذًا لَقَدْ كَانَ يَقُومُ حِينَ يَطْلُعُ الْفَجْرُ ‏.‏ قَالَ أَجَلْ ‏.‏

Yahya related to me from Malik from Hisham ibn Urwa that his father heard Abdullah ibn Amir ibn Rabia say, "We prayed subh behind Umar ibn al-Khattab and he recited suraYusuf (Sura 12) and surat al- Hajj (Sura 22) slowly." I (Hisham's father) said, "By Allah, then it must have been his habit to get up at the crack of dawn." He said, "Of course

Reference

Muwatta Malik 182

In-book

Book 3, Hadith 15