Sayyiduna Adi bin Hatim (may Allah be pleased with him) said: I said: O Messenger of Allah! Tell me about the saying of Allah Almighty: "The white thread from the black thread" [Surah al-Baqarah: 187], does it really mean two threads? The Messenger of Allah (peace and blessings be upon him) smiled and said: "No, rather it means the whiteness of the day and the blackness of the night."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14249