The Torah says that Terach died before Lech Lecha, even though he actually passed away years later, because
- When Avraham left, Terach returned to his wicked ways. Death =serving idols
- So that people wouldn't say that Avraham didn't have Kibbud Av.
- With Avraham gone, it was considered as if Terach was dead.
- אין מוקדם ומאוחר בתורה - it doesn't have to go in order
