"Allah has sent down the best of speech," meaning: the Quran. "A consistent book," meaning: its parts resemble one another in their light, truthfulness, and justice. "Mathani (oft-repeated)," meaning: Allah has repeated the stories in it, mentioning Paradise in this surah and then repeating the mention of it in another surah, and mentioning the Fire in this surah then mentioning it in other surahs; this is the tafsir of al-Hasan.

Muhammad said: "Mathani" is an adjective for the word "a book" (kitaban) and it is diptote (ghayr munsarif); because it is a broken plural that does not follow...