Charles Ellicott Commentary Joshua 14:7

"Forty years old was I when Moses the servant of Jehovah sent me from Kadesh-barnea to spy out the land; and I brought him word again as it was in my heart." — Joshua 14:7 (ASV)

Forty years old was I... and I am this day fourscore and five years old (Joshua 14:7, 10). In this speech we have the only direct evidence as to the duration of the wars of Canaan under Joshua.

The spies were sent from Kadesh-barnea in the second year of the Exodus, about 38½ years before the passage of the Jordan . Thus Caleb would be 40+38=78 years old when they crossed the Jordan. He was 85 when they began to divide the country.

Therefore, the conquest itself must have extended over a period of seven years. It is manifest that the record of the capture of Jericho and Ai, with the two campaigns of Joshua against the southern and northern confederacies, does not give all the details of the war.