Leviticus 26:32-34a

"I will bring the land (that is the Promised Land) into desolation: your enemies which dwell therein shall be astonished at it. (That is the desolation. In God's own time, He says) 33. I will scatter you among the heathen, (that is the non-Jewish world, what we call Gentiles) and I will draw out a sword after you: (They're going to suffer persecution.) and your land shall be desolate, your cities waste. 34. Then shall the land (that is the Promised Land) enjoy her sabbaths,..." Now, this is a direct reference to the 70-year captivity. The sabbatical year was when every seventh year the ground was to be left fallow; given a rest, and they never did it. So, over a period of 490 years neglecting the sabbatical year, they owed God 70 years. So, God is going to get those years back.