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 d

Samura b. Jundub addressed and narrated from the Messenger of Allah (ﷺ) having said (these words):

Neither the call of Bilal should mislead you nor this whiteness (of false dawn) till (the true) dawn appears (or he said) till the dawn breaks.
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ سَوَادَةَ، قَالَ سَمِعْتُ سَمُرَةَ، بْنَ جُنْدَبٍ - رضى الله عنه - وَهُوَ يَخْطُبُ يُحَدِّثُ عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ قَالَ ‏ "‏ لاَ يَغُرَّنَّكُمْ نِدَاءُ بِلاَلٍ وَلاَ هَذَا الْبَيَاضُ حَتَّى يَبْدُوَ الْفَجْرُ - أَوْ قَالَ - حَتَّى يَنْفَجِرَ الْفَجْرُ ‏"‏ ‏.‏
Reference : Sahih Muslim 1094d
In-book reference : Book 13, Hadith 53
USC-MSA web (English) reference : Book 6, Hadith 2410
  (deprecated numbering scheme)