Adi b. Hatim (Allah be pleased with him) reported that when (this verse) was revealed:
Until the white streak of the dawn becomes distinct from the dark streak (ii. 187) Adi b. Hatim said: Messenger of Allah, verily I keep underneath my pillow two strings, one white and the other black, by which I distinguish night from dawn. Upon this the Messenger of Allah ( صلی اللہ علیہ وسلم ) said: Your pillow seems to be very large. For the word khait implies the blackness of the night and the whiteness of the dawn.