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
jos 8:1GOD ENCOURAGES JOSHUA. (Jos. 8:1-28)
The Lord said unto Joshua, Fear not--By the execution of justice on Achan, the divine wrath was averted, the Israelites were reassured, defeat was succeeded by victory; and thus the case of Ai affords a striking example of God's disciplinary government, in which chastisements for sin are often made to pave the way for the bestowment of those temporal benefits, which, on account of sin, have been withdrawn, or withheld for a time. Joshua, who had been greatly dispirited, was encouraged by a special communication promising him (see Jos 1:6; Deu 31:6-8) success in the next attempt, which, however, was to be conducted on different principles.
take all the people of war with thee, and arise, go up to Ai--The number of fighting men amounted to six hundred thousand, and the whole force was ordered on this occasion, partly because the spies, in their self-confidence, had said that a few were sufficient to attack the place (Jos 7:3), partly to dispel any misgivings which the memory of the late disaster might have created, and partly that the circumstance of the first spoil obtained in Canaan being shared among all, might operate both as a reward for obedience in refraining from the booty of Jericho, and as an incentive to future exertions (Deu 6:10). The rest of the people, including the women and children, remained in the camp at Gilgal. Being in the plains of Jericho, it was an ascent to Ai, which was on a hill.
I have given into thy hand the king of Ai, and his people, and his city, and his land . . . lay thee an ambush for the city--God assured Joshua of Ai's capture, but allowed him to follow his own tactics in obtaining the possession.
jos 8:3So Joshua . . . chose out thirty thousand mighty men of valour--Joshua despatched thirty thousand men under cover of night, to station themselves at the place appointed for the ambuscade. Out of this number a detachment of five thousand was sent forward to conceal themselves in the immediate precincts of the town, in order to seize the first opportunity of throwing themselves into it [Jos 8:12].
jos 8:4behind the city--is rendered (Jos 8:9), "on the west side of Ai."
jos 8:9between Beth-el and Ai--Beth-el, though lying quite near in the direction of west by north, cannot be seen from Tell-el-hajar; two rocky heights rise between both places, in the wady El-Murogede, just as the laying of an ambush to the west of Ai would require [VAN DE VELDE; ROBINSON].
jos 8:10Joshua . . . numbered the people--that is, the detachment of liers-in-wait; he did this, to be furnished with clear evidence afterwards, that the work had been done without any loss of men, whereby the people's confidence in God would be strengthened and encouragement given them to prosecute the war of invasion with vigor.
he and the elders of Israel--the chief magistrates and rulers, whose presence and official authority were necessary to ensure that the cattle and spoil of the city might be equally divided between the combatants and the rest of the people (Num 31:27) --a military rule in Israel, that would have been very liable to be infringed, if an excited soldiery, eager for booty, had been left to their own will.
jos 8:11there was a valley between them and Ai--literally, "the valley."
jos 8:13Joshua went that night into the midst of the valley--The deep and steep-sided glen to the north of Tell-el-hajar, into which one looks down from the tell, fully agrees with this account [VAN DE VELDE]. Joshua himself took up his position on the north side of "the ravine"--the deep chasm of the wady El-Murogede; "that night"--means, while it was dark, probably after midnight, or very early in the morning (Joh 20:1). The king of Ai, in the early dawn, rouses his slumbering subjects and makes a hasty sally with all his people who were capable of bearing arms, once more to surprise and annihilate them.
jos 8:14at a time appointed--either an hour concocted between the king and people of Ai and those of Beth-el, who were confederates in this enterprise, or perhaps they had fixed on the same time of day, as they had fought successfully against Israel on the former occasion, deeming it a lucky hour (Jdg 20:38).
but he wist not that there were liers in ambush against him behind the city--It is evident that this king and his subjects were little experienced in war; otherwise they would have sent out scouts to reconnoitre the neighborhood; at all events, they would not have left their town wholly unprotected and open. Perhaps an ambuscade may have been a war stratagem hitherto unknown in that country, and among that people.
jos 8:15Joshua and all Israel made as if they were beaten before them--the pretended flight in the direction of the wilderness; that is, southeast, into the Ghor, the desert valley of the Jordan, decoyed all the inhabitants of Ai out of the city, while the people of Beth-el hastened to participate in the expected victory. It is supposed by some, from "the city," and not "cities," being spoken of, that the effective force of Beth-el had been concentrated in Ai, as the two places were closely contiguous, and Ai the larger of the two. (See Jos 12:9). It may be remarked, however, that the words, "or Beth-el," are not in the Septuagint, and are rejected by some eminent scholars, as an interpolation not found in the most ancient manuscripts.
jos 8:18Joshua stretched out the spear that he had in his hand toward the city--The uplifted spear had probably a flag, or streamer on it, to render it the more conspicuous from the height where he stood. At the sight of this understood signal the ambush nearest the city, informed by their scouts, made a sudden rush and took possession of the city, telegraphing to their brethren by raising a smoke from the walls. Upon seeing this, the main body, who had been reigning a flight, turned round at the head of the pass upon their pursuers, while the twenty-five thousand issuing from their ambuscade, fell back upon their rear. The Ai-ites surprised, looked back, and found their situation now desperate.
jos 8:23the king of Ai they took alive, and brought him to Joshua--to be reserved for a more ignominious death, as a greater criminal in God's sight than his subjects. In the mingled attack from before and behind, all the men were massacred.
jos 8:24all the Israelites returned unto Ai, and smote it with the edge of the sword--the women, children, and old persons left behind, amounting, in all, to twelve thousand people [Jos 8:25].
jos 8:26Joshua drew not his hand back--Perhaps, from the long continuance of the posture, it might have been a means appointed by God, to animate the people, and kept up in the same devout spirit as Moses had shown, in lifting up his hands, until the work of slaughter had been completed--the ban executed. (See on Exo 17:10).
jos 8:28Joshua burnt Ai, and made it an heap for ever--"For ever" often signifies "a long time" (Gen 6:3). One of the remarkable things with regard to the tell we have identified with Ai is its name--the tell of the heap of stones--a name which to this day remains [VAN DE VELDE].
jos 8:29THE KING HANGED. (Jos 8:29)
The king of Ai he hanged on a tree until eventide--that is, gibbeted. In ancient, and particularly Oriental wars, the chiefs, when taken prisoners, were usually executed. The Israelites were obliged, by the divine law, to put them to death. The execution of the king of Ai would tend to facilitate the conquest of the land, by striking terror into the other chiefs, and making it appear a judicial process, in which they were inflicting the vengeance of God upon His enemies.
take his carcass down . . . and raise thereon a great heap of stones--It was taken down at sunset, according to the divine command (Deu 21:23), and cast into a pit dug "at the entering of the gate," because that was the most public place. An immense cairn was raised over his grave--an ancient usage, still existing in the East, whereby is marked the sepulchre of persons whose memory is infamous.
jos 8:30JOSHUA BUILDS AN ALTAR. (Jos 8:30-31)
Then Joshua built an altar unto the Lord God of Israel in mount Ebal--(See on Deu 27:11). This spot was little short of twenty miles from Ai. The march through a hostile country and the unmolested performance of the religious ceremonial observed at this mountain, would be greatly facilitated, through the blessing of God, by the disastrous fall of Ai. The solemn duty was to be attended to at the first convenient opportunity after the entrance into Canaan (Deu 27:2); and with this in view Joshua seems to have conducted the people through the mountainous region that intervened though no details of the journey have been recorded. Ebal was on the north, opposite to Gerizim, which was on the south side of the town Sichem (Nablous).
jos 8:31an altar of whole stones--according to the instructions given to Moses (Exo 20:25; Deu 27:5).
over which no man hath lifted up any iron--that is, iron tool. The reason for this was that every altar of the true God ought properly to have been built of earth (Exo 20:24); and if it was constructed of stone, rough, unhewn stones were to be employed that it might retain both the appearance and nature of earth, since every bloody sacrifice was connected with sin and death, by which man, the creature of earth, is brought to earth again [KEIL].
they offered thereon burnt offerings unto the Lord, and sacrificed peace offerings--This had been done when the covenant was established (Exo 24:5); and by the observance of these rites (Deu 27:6), the covenant was solemnly renewed--the people were reconciled to God by the burnt offering, and this feast accompanying the peace or thank offering, a happy communion with God was enjoyed by all the families in Israel.
jos 8:32he wrote there upon the stones a copy of the law of Moses--(See on Deu 27:2-3, Deu 27:5); that is, the blessings and curses of the law. Some think that the stones which contained this inscription were the stones of the altar: but this verse seems rather to indicate that a number of stone pillars were erected alongside of the altar, and on which, after they were plastered, this duplicate of the law was inscribed.
jos 8:33all Israel, and their elders, and officers, and their judges, stood on this side the ark and on that side--One half of Israel was arranged on Gerizim, and the other half on Ebal--along the sides and base of each.
before the priests the Levites--in full view of them.
jos 8:34afterward he read all the words of the law--caused the priests or Levites to read it (Deu 27:14). Persons are often said in Scripture to do that which they only command to be done.
jos 8:35There was not a word of all that Moses commanded, which Joshua read not--It appears that a much larger portion of the law was read on this occasion than the brief summary inscribed on the stones; and this must have been the essence of the law as contained in Deuteronomy (Deu 4:44; Deu 6:9; Deu 27:8). It was not written on the stones, but on the plaster. The immediate design of this rehearsal was attained by the performance of the act itself. It only related to posterity, in so far as the record of the event would be handed down in the Book of Joshua, or the documents which form the groundwork of it [HENGSTENBERG]. Thus faithfully did Joshua execute the instructions given by Moses. How awfully solemn must have been the assemblage and the occasion! The eye and the ear of the people being both addressed, it was calculated to leave an indelible impression; and with spirits elevated by their brilliant victories in the land of promise, memory would often revert to the striking scene on mounts Ebal and Gerizim, and in the vale of Sychar.