أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا الْمُعْتَمِرُ بْنُ سُلَيْمَانَ، عَنْ أَبِيهِ، عَنْ أَبِي عُثْمَانَ، عَنِ ابْنِ مَسْعُودٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ إِنَّ بِلاَلاً يُؤَذِّنُ بِلَيْلٍ لِيُوقِظَ نَائِمَكُمْ وَلِيَرْجِعَ قَائِمَكُمْ وَلَيْسَ أَنْ يَقُولَ هَكَذَا ‏"‏ ‏.‏ يَعْنِي فِي الصُّبْحِ ‏.‏

It was narrated from Ibn Mas'ud that the Prophet (S.A.W) said: "Bilal calls the Adhan during the night to wake those who are sleeping and so that those who are praying Qiyam can return.

Meaning to finish. Ash-Shawkani said: "To return to sleeping or return to sitting from praying" Nail Al-Awtar.

Indicating with an up and down motion. The true dawn is from right to left.