Narrated 'Abdullah bin Mas'ud: The Prophet (ﷺ) said, "The call (or the Adhan) of Bilal 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 No. 5298
Sahih al Bukhari