Forty years — It rested about forty years, or the greatest part of forty years: it being most frequent in scripture to use numbers in such a latitude. Nor is it unusual either in scripture, or in other authors, for things to be denominated from the greater part; especially, when they enjoyed some degrees of rest and peace even in their times of slavery.
Related Commentaries of Judges 3:11
Judges 3:11
11 And the land had rest forty years. And Othniel the son of Kenaz died.