Aaron was 123 years old when he died on Mount Hor.
Aaron the priest obeyed the Lord and went up Mount Hor. Aaron died at that place on the first day of the fifth month. That was the 40th year after the Israelites had left Egypt.
Arad was a town in the Negev, in the land of Canaan. The Canaanite king in that place heard that the Israelites were coming.
Moses was 80 years old at the time, and Aaron was 83.