Narrated 'Adi bin Hatim:
"When 'Until the white (light) thread of dawn appears distinct to you from the black thread (of night)' was revealed, the Prophet (ﷺ) said to me: 'That only refers to the whiteness of the day from the blackness of the night.'" (ID)
English reference (ID): Vol. 5, Book 44, Hadith 2970 (ID)
Arabic reference (ID): Book 47, Hadith 3233 (ID)