Sahih al-Bukhari 1916
Book 30: Fasting · Hadith 26
Hadith text
Narrated `Adi bin Hatim:When the above verses were revealed: 'Until the white thread appears to you, distinct from the black thread,' I took two (hair) strings, one black and the other white, and kept them under my pillow and went on looking at them throughout the night but could not make anything out of it. So, the next morning I went to Allah's Messenger (ﷺ) and told him the whole story. He explained to me, "That verse means the darkness of the night and the whiteness of the dawn
Adi bin Hatim bataate hain: Jab upar wali ayaat nazil hui: "Jab tak tumhe safed dhaaga kaale dhaage se alag saaf dikhe," maine do (baalon ke) dhaage liye, ek kaala aur ek safed, aur unhe apne takiye ke neeche rakh liya aur poori raat unhe dekhta raha magar kuch samajh na paya. Agli subah main Allah ke Rasool ke paas gaya aur unhe poori baat batai. Unhone mujhe samjhaaya: "Iss ayat ka matlab hai raat ka andhera aur subah ki roshni."
Sahih al-Bukhari 1916 · Book 30, Hadith 26