Hebrews 9:4 says whose staff that had budded was kept inside the ark?

Answer: Aaron's

Inside the ark were the gold jar of manna, Aaron's staff that had budded, and the stone tablets of the covenant.

“containing the golden altar of incense and the gold-covered ark of the covenant. Inside the ark were the gold jar of manna, Aaron’s staff that had budded, and the stone tablets of the covenant.”— Hebrews 9:4 (BSB)