Surah 5. Al-Ma'ida, Ayah 26

The punishment of the rebellion of these stiff-necked people, rebellion that was repeated "these ten times" (Num. xiv. 22) and more, was that they were left to wander distractedly hither and thither through the wilderness for forty years. That generation was not to see the Holy Land. All those that were twenty years old and upwards were to die in the wilderness: "your carcasses shall fail in this wilderness." (Num. xiv. 29). Only those who were then children would reach the Promised land. And so it happened. From the desert of Paran they wandered south, north, and east for forty years. From the head of what is now the Gulf of 'Aqaba, they travelled north, keeping to the east side of the depression of which the Dead Sea and the river Jordan are portions. Forty years afterwards they crossed the Jordan opposite what is now Jericho, but by that time Moses, Aaron, and the whole of the elder generation had died.