Numbers 33:38-39

38Aaron the priest went up Mount Hor at the command of the Lord and died there in the fortieth year after the Israelites had come out of the land of Egypt, on the first day of the fifth month. 39Aaron was one hundred twenty-three years old when he died on Mount Hor.

From the oremus Bible Browser https://bible.oremus.org v2.5.1 29 April 2019.