"Bilal calls the Adhan during the night to wake those who are sleeping and so that those who are praying Qiyam can return.[1] Not to say it is like this." The break of dawn is not like this. [2] [1] Meaning to finish. Ash-Shawkani said: "To return to sleeping or return to sitting from praying" Nail Al-Awtar. [2] Indicating with an up and down motion. The true dawn is from right to left. (Using translation from Nasāʾī 641)  

عَنِ النَّبِيِّ ﷺ قَالَ «إِنَّ بِلَالًا يُؤَذِّنُ بِلَيْلٍ لِيُوقِظَ نَائِمَكُمْ وَلِيَرْجِعَ قَائِمَكُمْ وَلَيْسَ أَنْ يَقُولَ هَكَذَا يَعْنِي الصُّبْحَ»