Sunan An-Nasai, Chapter: The Book of the Adhan (The Call to Prayer)

that the Prophet (saw) said: "Bilal calls the Adhan during the night to wake those who are sleeping and so that those who are praying Qiyam can return.* Not to say it is like this." The break of dawn is not like this.** *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.