This Bible contradiction is from the Skeptic's Annotated Bible.
Genesis 22:14 View context
And Abraham called the name of that place Jehovah-jireh: as it is said [to] this day, In the mount of the LORD it shall be seen.
Exodus 6:3 View context
And I appeared unto Abraham, unto Isaac, and unto Jacob, by [the name of] God Almighty, but by my name JEHOVAH was I not known to them.