"And before it"—meaning before the Quran—"was the Book of Moses as an imam [leader/guide]"—meaning the Torah—by which they are guided, "and a mercy"—to those who believed in it. "And this is a Book"—meaning the Quran—"confirming" the Torah and the Gospel, "in an Arabic tongue, to warn those who have done wrong"—that is, those who have associated partners with God—"and as glad tidings for the doers of good"—the believers—regarding Paradise.

Muhammad said: "Imaman" (an imam) is in the accusative case as a circumstantial qualifier (hal). "Wa rahmatan" (and a mercy) is conjoined to it. "Lisanan 'arabiyyan" (in an Arabic tongue) is also in the accusative case as a circumstantial qualifier; the meaning is: it confirms what was before it, being in Arabic, and he mentioned "lisanan" (tongue/language) as an emphasis.