Salim bin Abu Ubaid narrates: I was under the tutelage of Sayyiduna Abu Bakr Siddiq (may Allah be pleased with him). One night, he performed prayer for as long as Allah willed, then said: Has true dawn appeared? Salim narrates: I went outside and came back to inform him: There is whiteness in the sky going upwards (in a vertical direction). So Sayyiduna Abu Bakr Siddiq (may Allah be pleased with him) performed voluntary prayers for as long as Allah willed, then said: Go and see, has true dawn appeared? I went again and returned to reply that redness has spread across the sky in a horizontal direction. Then he said: Yes! Now the time has come, bring me my pre-dawn meal.