Sayyiduna Abdullah (bin Mas'ud) (may Allah be pleased with him) says: "By the One besides whom there is no god, there is no surah in the Book of Allah except that I know where it was revealed, and there is no verse in it except that I know concerning what it was revealed."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8400