Numbers 33:38

33:38 Aaron the priest ascended Mount Hor at the command of the Lord, and he 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.

Deuteronomy 1:3

1:3 However, it was not until the first day of the eleventh month of the fortieth year that Moses addressed the Israelites just as the Lord had instructed him to do.

Deuteronomy 2:14

2:14 Now the length of time it took for us to go from Kadesh Barnea to the crossing of Wadi Zered was thirty-eight years, time for all the military men of that generation to die, just as the Lord had vowed to them.