Translation:

19. O people of the Book! now hath come unto you making (things) clear unto you Our Apostle after the break in (the series of) Our apostles lest ye should say: there came unto us no bringer of glad tidings and no warner (from evil): but now hath come unto you a bringer of glad tidings and a warner (from evil): and Allah hath power over all things.

Notes (Tafseer)

720. The six hundred years (in round figures) between Christ and Muhammad were truly the dark ages of the world. Religion was corrupted: the standard of morals fell low: many false systems and heresies arose; and there was a break in the succession of prophets until the advent of Muhammand.