Numbers 33:37-41

They journeyed from Kadesh and camped at Mount Hor, at the edge of the land of Edom.

Then Aaron the priest went up to Mount Hor at the command of the Lord, and died there in the fortieth year after the sons of Israel had come from the land of Egypt, on the first day in the fifth month.

Aaron was 123 years old when he died on Mount Hor.

Now the Canaanite, the king of Arad who lived in the Negev in the land of Canaan, heard about the coming of the sons of Israel.

Then they journeyed from Mount Hor and camped at Zalmonah.