Hadith 1928
It is narrated from Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: “None of you should let Bilal’s (may Allah be pleased with him) call to prayer prevent him from eating suhoor, because he gives the adhan so that the one who is sleeping may wake up and the one who is standing in prayer may return (home to eat suhoor).” The Prophet (peace and blessings be upon him) said: “Dawn does not appear in this way (lengthwise), rather it appears in this way, that is, widthwise.”
Hadith 1929
Sayyiduna Samurah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Do not be deceived by Bilal’s (may Allah be pleased with him) call to prayer or the vertical whiteness of the dawn (and thus stop eating the pre-dawn meal); continue until the (true) light of dawn spreads horizontally."