Narrated 'Abdullah bin Mas'ud: The Prophet said, "The call (or the Adhan) of Bila should not stop you from taking the Suhur-meals for Bilal calls (or pronounces the Adhan) so that the one who is offering the night prayer should take a rest, and he does not indicate the daybreak or dawn." The narrator, Yazid, described (how dawn breaks) by stretching out his hands and then separating them wide apart.
Hadith Referenceصحيح البخاري / كتاب الطلاق / 5298
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة
Brief Explanation
To understand the relevance between the chapter and the hadith, see the benefits and issues (fawa’id wa masail) of Sahih Bukhari hadith number 5293 by Shaykh Muhammad Husain Memon.