"Is he, then, upon a clear proof from his Lord?"—meaning: a clarification and certainty; he refers to Muhammad, peace be upon him. "And a witness from Him follows him"—the interpretation of al-Kalbi is: Gabriel is a witness from Allah, the Mighty and Majestic. "And before it"—meaning: before the Quran—"was the Book of Moses as an imam and a mercy"—meaning: for whoever believed in it.
He says: Is he who was upon a clear proof from his Lord, and is followed by a witness from Him, equal to one who disbelieves in the Quran, the Torah, and the Gospel? Meaning: they are not equal before Allah, the Mighty and Majestic.
Muhammad said: It is permissible to use the accusative case (nasb) for the words "as an imam and a mercy" as a state (hal).
"Those believe in it"—meaning: the believers believe in the Quran. "But whoever disbelieves in it among the factions"—Qatada said: Meaning the Jews and the Christians. "The Fire is his promised place. So do not be in doubt about it"—meaning: in doubt that whoever disbelieves in it, the Fire is his promised place.
Surah Hud, from verse (18) to verse (19).
