" 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 (ﷺ) said: Your pillow seems to be very large. For the word khait implies the blackness of the night and the whiteness of the dawn.
Sahih Muslim Book 13, Hadith 39
← Previous Hadith The months of 'Id are not incomplete. And in the hadith narrated by Khalid (the words are):" The months, of 'Id are Ramadan and Dhu'l-Hijja."

Sahih Muslim Book 13, Hadith 38 Next Hadith → " Eat and drink till the white streak is distinct from the dark streak," a person would take hold of a white thread and a black thread and keep on eating till he could find them distinct (in the light of the dawn). It was then that Allah, the Majestic and Great, reveiled (the words) min al-fajr (from the dawn), and then it became clear (that the word khait refers to the streak of light in the dawn).

Sahih Muslim Book 13, Hadith 40