A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
jdg 13:1ISRAEL SERVES THE PHILISTINES FORTY YEARS. (Jdg 13:1)
the Lord delivered them into the hand of the Philistines forty years--The Israelites were represented (Jdg 10:6-7) as having fallen universally into a state of gross and confirmed idolatry, and in chastisement of this great apostasy, the Lord raised up enemies that harassed them in various quarters, especially the Ammonites and Philistines. The invasions and defeat of the former were narrated in the two chapters immediately preceding this; and now the sacred historian proceeds to describe the inroads of the latter people. The period of Philistine ascendency comprised forty years, reckoning from the time of Elon till the death of Samson.
jdg 13:2AN ANGEL APPEARS TO MANOAH'S WIFE. (Jdg 13:2-10)
Zorah--a Danite town (Jos 15:33) lying on the common boundary of Judah and Dan, so that it was near the Philistine border.
jdg 13:3the angel of the Lord--The messenger of the covenant, the divine personage who made so many remarkable appearances of a similar kind already described.
jdg 13:5thou shalt conceive, and bear a son--This predicted child was to be a Nazarite. The mother was, therefore, for the sake of her promised offspring, required to practice the rigid abstinence of the Nazarite law (see on Num 6:2).
he shall begin to deliver Israel out of the hand of the Philistines--a prophecy encouraging to a patriotic man; the terms of it, however, indicated that the period of deliverance was still to be distant.
jdg 13:6then Manoah entreated the Lord--On being informed by his wife of the welcome intimation, the husband made it the subject of earnest prayer to God. This is a remarkable instance, indicative of the connection which God has established between prayer and the fulfilment of His promises.
jdg 13:11THE ANGEL APPEARS TO MANOAH. (Jdg 13:11-14)
Art thou the man that spakest unto the woman?--Manoah's intense desire for the repetition of the angel's visit was prompted not by doubts or anxieties of any kind, but was the fruit of lively faith, and of his great anxiety to follow out the instructions given. Blessed was he who had not seen, yet had believed.
jdg 13:15MANOAH'S SACRIFICE. (Jdg 13:15-23)
Manoah said unto the angel . . ., I pray thee, let us detain thee, until we shall have made ready a kid--The stranger declined the intended hospitality and intimated that if the meat were to be an offering, it must be presented to the Lord [Jdg 13:6]. Manoah needed this instruction, for his purpose was to offer the prepared viands to him, not as the Lord, but as what he imagined him to be, not even an angel (Jdg 13:16), but a prophet or merely human messenger. It was on this account, and not as rejecting divine honors, that he spoke in this manner to Manoah. The angel's language was exactly similar to that of our Lord (Mat 19:17).
jdg 13:17Manoah said unto the angel . . ., What is thy name?--Manoah's request elicited the most unequivocal proofs of the divinity of his supernatural visitor--in his name "secret" (in the Margin, "wonderful"), and in the miraculous flame that betokened the acceptance of the sacrifice.
jdg 13:24SAMSON BORN. (Jdg 13:24-25)
the woman bare a son, and called his name Samson--The birth of this child of promise, and the report of the important national services he was to render, must, from the first, have made him an object of peculiar interest and careful instruction.
jdg 13:25the Spirit of the Lord began to move him at times--not, probably, as it moved the prophets, who were charged with an inspired message, but kindling in his youthful bosom a spirit of high and devoted patriotism.
Eshtaol--the free city. It, as well as Zorah, stood on the border between Judah and Dan.