Isaiah 48:20

In view of the new promises concerning Cyrus and return from exile, Isaiah called on the Israelites in captivity to depart from Babylon when they could (cf. Revelation 18:4-5), and to publicize the promise of the second Exodus. It was as good as accomplished. In view of this prophecy, it was wrong for the Israelites to remain in Babylonia after Cyrus permitted them to return to the Promised Land. Yet many did remain.

This verse is, "A summons beforehand to Jews who would be captives in 539 B.C. not to tarry in the pagan soil of Babylon, but to take advantage of Cyrus’ permissive edict and return to Judah." [Note: Archer, p. 643.]

This "missionary challenge" to take good news to the nations fittingly climaxes the message of chapters 40-48.