Narrated 'Abd Allah b. Mas'ud:
The Messenger of Allah (ﷺ) as saying: The summons (adhan) of Bilal should not restrain one of you from taking a meal shortly before dawn, for he utters adhan or calls (for prayer) so that the man at prayer may return, and the man asleep may get up. Dawn is not (the whiteness) which indicates thus (in perpendicular) - the narrator Musaddad said: Yahya joined his palms (indicating the spread of whiteness vertically - until it indicates thus - and Yahya spread out two ring-fingers of his (demonstrating the spread of whiteness horizontally)l