'Forty Years' in the Bible

So the land had rest forty years. Then Oth'ni-el the son of Kenaz died.

"So perish all thine enemies, O LORD! But thy friends be like the sun as he rises in his might." And the land had rest for forty years.

So Mid'ian was subdued before the people of Israel, and they lifted up their heads no more. And the land had rest forty years in the days of Gideon.

And the people of Israel again did what was evil in the sight of the LORD; and the LORD gave them into the hand of the Philistines for forty years.