What did Moses ask God to do to him if He would not forgive Israel's sin?

Answer: Blot him out of His book

"If You would only forgive their sin.... But if not, please blot me out of the book that You have written."

“So Moses returned to the LORD and said, “Oh, what a great sin these people have committed! They have made gods of gold for themselves. Yet now, if You would only forgive their sin.... But if not, please blot me out of the book that You have written.””— Exodus 32:31-32 (BSB)