'Seventy' in the Bible

This whole land shall be a desolation, and an astonishment; and these nations shall serve the king of Babylon seventy years.

It shall happen, when seventy years are accomplished, that I will punish the king of Babylon, and that nation, says Yahweh, for their iniquity, and the land of the Chaldeans; and I will make it desolate forever.

For thus says Yahweh, After seventy years are accomplished for Babylon, I will visit you, and perform my good word toward you, in causing you to return to this place.