'Seventy' in the Bible

This entire land will be a desolation and a waste, and these nations will serve the king of Babylon for seventy years.

"Then when the seventy years have passed, I'll judge the king of Babylon and that nation, declares the LORD, I'll judge the land of the Chaldeans for their iniquity and I'll make it a desolation forever.

"For this is what the LORD says: "When Babylon's seventy years are completed, I'll take note of you and will fulfill my good promises to you by bringing you back to this place.