Numbers 33:38 in the World English Bible
Aaron the priest went up into Mount Hor at the commandment of the LORD and died there, in the fortieth year after the children of Israel had come out of the land of Egypt, in the fifth month, on the first day of the month.
Context
37 And they removed from Kadesh, and pitched in mount Hor, in the edge of the land of Edom.
38 And Aaron the priest went up into mount Hor at the commandment of the LORD, and died there, in the fortieth year after the children of Israel were come out of the land of Egypt, in the first day of the fifth month.
39 And Aaron was an hundred and twenty and three years old when he died in mount Hor.