Numbers 33:37-39

New Century Version

³⁷ They left Kadesh and camped at Mount Hor, on the border of Edom. ³⁸ Aaron the priest obeyed the Lord and went up Mount Hor. There he died on the first day of the fifth month in the fortieth year after the Israelites left Egypt. ³⁹ Aaron was 123 years old when he died on Mount Hor.