And he judgeth Israel in the days of the Philistines twenty years.

And he was judge of Israel in the days of the Philistines for twenty years.

He judged Israel - twenty years - In the margin it is said, He seems to have judged southwest Israel during twenty years of their servitude of the Philistines, Judges 13:1. Instead of עשרים שנה esrim shanah, twenty years, the Jerusalem Talmud has ארבעים שנה arbaim shanah, forty years; but this reading is not acknowledged by any MS. or version. According to Calmet, the twenty years of the judicature of Samson began the eighteenth year of the subjection of Israel to the Philistines; and these twenty years are included in the judicature of the high priest Eli.
The burning of the Philistines' corn by the means of foxes and firebrands is a very remarkable circumstance; and there is a story told by Ovid, in the 4th book of his Fasti, that bears a striking similitude to this; and is supposed by some learned men to allude to Samson and his foxes. The poet is at a loss to account for this custom, but brings in an old man of Carseoli, with what must have appeared to himself a very unsatisfactory solution. The passage begins as follows: -
Tertia post Hyadas cum luxerit orta, remotas,
Carcere partitos Circus habebit equos
Cur igitur missae vinctis ardentia taedis
Terga ferant vulpes, causa docenda mihi?
Vid. Ovid, Fastor. lib. iv., ver. 679.
The substance of the whole account, which is too long to be transcribed, is this: It was a custom in Rome, celebrated in the month of April to let loose a number of foxes in the circus, with lighted flambeaux on their backs; and the Roman people took pleasure in seeing these animals run about till roasted to death by the flames with which they were enveloped. The poet wishes to know what the origin of this custom was, and is thus informed by an old man of the city of Carseoli: "A frolicksome young lad, about ten years of age, found, near a thicket, a fox that had stolen away many fowls from the neighboring roosts. Having enveloped his body with hay and straw, he set it on fire, and let the fox loose. The animal, in order to avoid the flames, took to the standing corn which was then ready for the sickle; and the wind, driving the flames with double violence, the crops were everywhere consumed. Though this transaction is long since gone by, the commemoration of it still remains; for, by a law of this city, every fox that is taken is burnt to death. Thus the nation awards to the foxes the punishment of being burnt alive, for the destruction of the ripe corn formerly occasioned by one of these animals."
Both Serrarius and Bochart reject this origin of the custom given by Ovid; and insist that the custom took its rise from the burning of the Philistines' corn by Samson's foxes. The origin ascribed to the custom by the Carseolian they consider as too frivolous and unimportant to be commemorated by a national festival. The time of the observation does not accord with the time of harvest about Rome and in Italy, but it perfectly accords with the time of harvest in Palestine, which was at least as early as April. Nor does the circumstance of the fox wrapped in hay and let loose, the hay being set on fire, bear any proper resemblance to the foxes let loose in the circus with burning brands on their backs.
These learned men therefore conclude that it is much more natural to suppose that the Romans derived the custom from Judea, where probably the burning of the Philistines' corn might, for some time, have been annually commemorated.
The whole account is certainly very singular, and has not a very satisfactory solution in the old man's tale, as related by the Roman poet.
All public institutions have had their origin in facts; and if, through the lapse of time or loss of records, the original facts be lost, we may legitimately look for them in cases where there is so near a resemblance as in that above.

And he judged Israel in the days of the Philistines twenty years. While they had the power over the Israelites, who were not entirely delivered out of their hands by Samson, he only began to deliver them, but did not completely do it; though he got many advantages over them, and wrought many salvations and deliverances, yet was not the author of perfect salvation, see Judges 13:5 however, he was a check upon the Philistines, and protected the Israelites from heavier oppressions, which otherwise they would have come under; and no doubt administered justice and judgment among them, and was an instrument of their reformation, and of preserving them from idolatry; for in such things the work of a judge chiefly lay: some from hence observe, that this shows the years of servitude and bondage are included in the years of the judges.

He judged - That is, he pleaded their cause, and avenged them against the Philistines. Of the Philistines - That is, whilst the Philistines had the power and dominion, from which he was not fully to deliver, but only to begin to deliver them. From this place it is manifest, that in the computation of the times of the judges, the years of servitude or oppression are not to be separated from the years of the judges, but added to them, and are comprehended within them; which proposition is of great importance for clearing this difficult part of scripture - chronology.