Judges 13:1

And the children of Israel did evil in the sight of the Lord,.... Committed idolatry, which was the evil they were prone unto, and were frequently guilty of:

and the Lord delivered them into the hands of the Philistines forty years: which according to Josephus f are to be reckoned from the death of the last judge, and the time of Samson's birth; or rather from some time after the death of Jephthah, particularly taking in the two last years of Ibzan, when the Ephraimites having been weakened through the slaughter of them by Jephthah, might encourage the Philistines to break in upon them; from which time to the birth of Samson were twenty years, and twenty more may be allowed before he could begin to deliver Israel out of their hands; so that the oppression lasted forty years. According to others, it began at the same time as the oppression of the Ammonites did, though it lasted longer, Judges 10:7.

f Ibid. (Antiqu. l. 5.) c. 8. sect. 1.