عَنْ سَمُرَةَ بْنِ جُنْدُبٍ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((لَا يَمْنَعَنَّكُمْ مِنْ سَحُورِكُمْ أَذَانُ بِلَالٍ، وَلَا الْفَجْرُ الْمُسْتَطِيلُ، وَلَكِنِ الْفَجْرُ الْمُسْتَطِيرُ فِي الْأُفُقِ))
It is narrated from Sayyiduna Samurah bin Jundub (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: The adhan of Bilal (may Allah be pleased with him) and the false dawn should not prevent you from eating suhoor; but when the spreading light appears on the horizon, that is, the true dawn, then stop eating.