كتاب الصيام
13  
The Book of Fasting
(8)
Chapter: Clarifying that fasting begins at dawn, and a person may eat and other than that until dawn begins; And clarifying the dawn which has to do with the rulings concerning the beginning of fasting and the beginning of the time for the Subh Prayer, and other than that, which is the Second Dawn, which is called the True Dawn. The First Dawn, which is the False Dawn, has nothing to do with the rulings
(8)
بَاب بَيَانِ أَنَّ الدُّخُولَ فِي الصَّوْمِ يَحْصُلُ بِطُلُوعِ الْفَجْرِ وَأَنَّ لَهُ الْأَكْلَ وَغَيْرَهُ حَتَّى يَطْلُعَ الْفَجْرُ وَبَيَانِ صِفَةِ الْفَجْرِ الَّذِي تَتَعَلَّقُ بِهِ الْأَحْكَامُ مِنْ الدُّخُولِ فِي الصَّوْمِ وَدُخُولِ وَقْتِ صَلَاةِ الصُّبْحِ وَغَيْرِ ذَلِكَ
Sahih Muslim 1094 a

Samura b. Jandub reported Muhammad (ﷺ) as saying. The call of Bilal may not mislead any one of you (and he may, under the wrong impression gathered from it, refrain) from taking meal before the commencement of the fast (for the streaks) of this whiteness (which are vertical indicate the false dawn and the true dawn with which the fast commences is that when the streaks of light are) spread.

حَدَّثَنَا شَيْبَانُ بْنُ فَرُّوخَ، حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ عَبْدِ اللَّهِ بْنِ سَوَادَةَ الْقُشَيْرِيِّ، حَدَّثَنِي وَالِدِي، أَنَّهُ سَمِعَ سَمُرَةَ بْنَ جُنْدُبٍ، يَقُولُ سَمِعْتُ مُحَمَّدًا، صلى الله عليه وسلم يَقُولُ
Reference : Sahih Muslim 1094a
In-book reference : Book 13, Hadith 50
USC-MSA web (English) reference : Book 6, Hadith 2407
  (deprecated numbering scheme)