Until the land has enjoyed its sabbaths, it shall keep sabbath all the time of its desolation until the completion of seventy years: This is not an exact quotation from the book of Jeremiah. In Jer 25.11-12 and 29.10 the prophet speaks of a seventy-year-long period during which the land of Israel would be desolate (see also Lev 26.34-35). Lev 25.1-7 gives the law regarding Sabbaths for the land. The law was that farmland could be worked for six years, but in the seventh year, the Sabbath year, the land was to rest, and not be worked or planted. The meaning here is that the people have not been observing this law, and the land has many Sabbaths coming to it. Therefore the Lord is going to let the land have seventy years of rest by keeping the people in exile, away from the land. Good News Bible includes a footnote to help the reader understand what is meant by the land having a Sabbath rest. Most translators will find that such a footnote helps the reader. Here is an alternative model for this verse:

• “The people have not allowed the land to have its rest every seven years, so the Lord will give the land a long Sabbath rest.* It will lie empty and barren for seventy years.”
* Sabbath rest: This refers to Lev 25.1-7, which required that farmland was not to be worked every seventh year.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Esdras. (UBS Helps for Translators). Miami: UBS, 2019. For this and other handbooks for translators see here.