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 4:1DEBORAH AND BARAK DELIVER ISRAEL FROM JABIN AND SISERA. (Jdg. 4:1-17)
The children of Israel again did evil in the sight of the Lord, when Ehud was dead--The removal of the zealous judge Ehud again left his infatuated countrymen without the restraint of religion.
jdg 4:2Jabin king of Canaan--"Jabin," a royal title (see on Jos 11:1). The second Jabin built a new capital on the ruins of the old (Jos 11:10-11). The northern Canaanites had recovered from the effect of their disastrous overthrow in the time of Joshua, and now triumphed in their turn over Israel. This was the severest oppression to which Israel had been subjected. But it fell heaviest on the tribes in the north, and it was not till after a grinding servitude of twenty years that they were awakened to view it as the punishment of their sins and to seek deliverance from God.
jdg 4:4And Deborah, a prophetess--A woman of extraordinary knowledge, wisdom, and piety, instructed in divine knowledge by the Spirit and accustomed to interpret His will; who acquired an extensive influence, and was held in universal respect, insomuch that she became the animating spirit of the government and discharged all the special duties of a judge, except that of military leader.
the wife of Lapidoth--rendered by some, "a woman of splendors."
jdg 4:5she dwelt under the palm tree--or, collectively, "palm-grove." It is common still in the East to administer justice in the open air, or under the canopy of an umbrageous tree.
jdg 4:6she sent and called Barak--by virtue of her official authority as judge.
Kedesh-naphtali--situated on an eminence, little north of the Sea of Galilee, and so called to distinguish it from another Kedesh in Issachar.
Hath not the Lord God of Israel commanded?--a Hebrew form of making an emphatic communication.
Go and draw toward mount Tabor--an isolated mountain of Galilee, northeast corner of the plain of Esdraelon. It was a convenient place of rendezvous, and the enlistment is not to be considered as limited to ten thousand, though a smaller force would have been inadequate.
jdg 4:8Barak said unto her, If thou wilt go with me, then I will go--His somewhat singular request to be accompanied by Deborah was not altogether the result of weakness. The Orientals always take what is dearest to the battlefield along with them; they think it makes them fight better. The policy of Barak, then, to have the presence of the prophetess is perfectly intelligible as it would no less stimulate the valor of the troops, than sanction, in the eyes of Israel, the uprising against an oppressor so powerful as Jabin.
jdg 4:9the Lord shall sell Sisera into the hand of a woman--This was a prediction which Barak could not understand at the time; but the strain of it conveyed a rebuke of his unmanly fears.
jdg 4:11Now Heber the Kenite . . . pitched his tent--It is not uncommon, even in the present day, for pastoral tribes to feed their flocks on the extensive commons that lie in the heart of inhabited countries in the East (see on Jdg 1:16).
plain of Zaanaim--This is a mistranslation for "the oaks of the wanderers." The site of the encampment was under a grove of oaks, or terebinths, in the upland valley of Kedesh.
jdg 4:13the river of Kishon--The plain on its bank was chosen as the battlefield by Sisera himself, who was unconsciously drawn thither for the ruin of his army.
jdg 4:14Barak went down from mount Tabor--It is a striking proof of the full confidence Barak and his troops reposed in Deborah's assurance of victory, that they relinquished their advantageous position on the hill and rushed into the plain in face of the iron chariots they so much dreaded.
jdg 4:15the Lord discomfited Sisera--Hebrew, "threw his army into confusion"; men, horses, and chariots being intermingled in wild confusion. The disorder was produced by a supernatural panic (see on Jdg 5:20).
so that Sisera lighted down off his chariot, and fled away on his feet--His chariot being probably distinguished by its superior size and elegance, would betray the rank of its rider, and he saw therefore that his only chance of escape was on foot.
jdg 4:16But Barak pursued . . . unto Harosheth--Broken and routed, the main body of Sisera's army fled northward; others were forced into the Kishon and drowned (see on Jdg 5:21).
jdg 4:17Sisera fled . . . to the tent of Jael--According to the usages of nomadic people, the duty of receiving the stranger in the sheik's absence devolves on his wife, and the moment the stranger is admitted into his tent, his claim to be defended or concealed from his pursuers is established.
jdg 4:19she . . . gave him drink, and covered him--Sisera reckoned on this as a pledge of his safety, especially in the tent of a friendly sheik. This pledge was the strongest that could be sought or obtained, after he had partaken of refreshments, and been introduced in the inner or women's apartment.
jdg 4:20he said unto her, . . . when any man doth come and enquire of thee and say, Is there any man here? that thou shalt say, No--The privacy of the harem, even in a tent, cannot be intruded on without express permission.
jdg 4:21Then Jael took a nail of the tent--most probably one of the pins with which the tent ropes are fastened to the ground. Escape was almost impossible for Sisera. But the taking of his life by the hand of Jael was murder. It was a direct violation of all the notions of honor and friendship that are usually held sacred among pastoral people, and for which it is impossible to conceive a woman in Jael's circumstances to have had any motive, except that of gaining favor with the victors. Though predicted by Deborah [Jdg 4:9], it was the result of divine foreknowledge only--not the divine appointment or sanction; and though it is praised in the song [Jdg 5:24-27], the eulogy must be considered as pronounced not on the moral character of the woman and her deed, but on the public benefits which, in the overruling providence of God, would flow from it.