This Bible contradiction is from the Skeptic's Annotated Bible.

Verses

70 years

Jeremiah 29:10 View context

For thus saith the LORD, That after seventy years be accomplished at Babylon I will visit you, and perform my good word toward you, in causing you to return to this place.

Seven generations

Baruch 6:2 View context

When you are come into Babylon, you shall be there many years, and for a long time, even to seven generations.