'Fourth Generation' in the Bible

And Jehovah said unto Jehu, Because thou hast done well in executing that which is right in mine eyes, and hast done unto the house of Ahab according to all that was in my heart, thy sons of the fourth generation shall sit on the throne of Israel.

This was the word of Jehovah which he spake unto Jehu, saying, Thy sons to the fourth generation shall sit upon the throne of Israel. And so it came to pass.