بُلُوغُ الْمَرَامِ
Bulugh al-Maram 169
The Book of Prayer
وَعَنْ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ اَلْفَجْرُ فَجْرَانِ: فَجْرٌ يُحَرِّمُ اَلطَّعَامَ وَتَحِلُّ فِيهِ اَلصَّلَاةُ, وَفَجْرٌ تَحْرُمُ فِيهِ اَلصَّلَاةُ - أَيْ: صَلَاةُ اَلصُّبْحِ - وَيَحِلَّ فِيهِ اَلطَّعَامُ } رَوَاهُ اِبْنُ خُزَيْمَةَ, وَالْحَاكِمُ, وَصَحَّحَاهُ [1] .
Narrated Ibn 'Abbas (RA): Allah's Messenger (ﷺ) said that, "Dawn is of two types; the dawn in which eating is forbidden (for the fasting person) and prayer is permitted and the dawn in which prayer is forbidden i.e. the morning prayer and eating is permitted." [Reported by Ibn Khuzaimah and al-Hakim who (both) graded it Sahih].
Sunnah.com reference: Book 2, Hadith 21