To Christian men especially, failure brings very valuable lessons. There is always something to be learned from it. In our first attempt we were too self-confident. We went too carelessly about the matter, and did not sufficiently realize the need of Divine support. Never was there a servant of God who learned more from his failures than St. Peter. Nothing could have been more humiliating than his thrice-repeated denial of his Lord. But when Peter came to himself, he saw on what a bruised reed he had been leaning when he said, "Though I should die with Thee yet will I not deny Thee." How miserably misplaced that self-confidence had been! But it had the effect of startling him, of showing him his danger, and of leading him to lift up his eyes to the hills from whence came his help. It might have seemed a risky, nay reckless thing for our Lord to commit the task of steering His infant Church over the stormy seas of her first voyage to a man who, six weeks before, had proved so weak and treacherous. But Peter was a genuine man, and it was that first failure that afterwards made him so strong. It is no longer Peter, but Christ in Peter that directs the movement. And thus it came to pass that, during the critical period of the Church's birth, no carnal drawback diminished his strength or diluted his faith; all his natural rapidity of movement, all his natural outspokenness, boldness, and directness were brought to bear without abatement on the advancement of the young cause. He conducted himself during this most delicate and vital period with a nobility beyond all praise. He took the ship out into the open sea amid raging storms without touching a single rock. And it was all owing to the fact that by God's grace he profited by his failure!
In the case of Joshua and his people, one of the chief lessons derived from their failure before Ai was the evil of covering sin. Alas, this policy is the cause of failures innumerable in the spiritual life! In numberless ways it interrupts Divine fellowship, withdraws the Divine blessing, and grieves the Holy Spirit. We have not courage to cut off a right hand and pluck out a right eye. We leave besetting sins in a corner of our hearts, instead of trying to exterminate them, and determining not to allow them a foothold there. The acknowledgment of sin, the giving up of all leniency towards it, the determination, by God's grace, to be done with it, always go before true revivals, before a true return of God to us in all His graciousness and power. Rather, we should say, they are the beginning of revival. In Israel of old the land had to be purged of every vestige of idolatry under Hezekiah and other godly kings, before the light of God's countenance was again lifted upon it. "To this man will I look, even to him that is poor and of a contrite spirit, and that trembleth at My word."
Joshua is instructed to go up again against Ai, but in order to interest and encourage the people, he resorts to a new plan of attack. A stratagem is to be put in operation. An ambuscade is to be stationed on the west side of the city, while the main body of the assaulting force is to approach it, as formerly, from the east. There is some obscurity and apparent confusion in the narrative, confined, however, to one point, the number composing the ambuscade and the main body respectively. Some error in the text appears to have crept in. From the statement in ver. 3 we might suppose that the men who were to lie in ambush amounted to thirty thousand; but in ver. 12 it is expressly stated that only five thousand were employed in this way. There can be little doubt (though it is not according to the letter of the narrative) that the whole force employed amounted to thirty thousand, and that, of these, five thousand formed the ambush. Indeed, in such a valley, it would not have been possible for thirty thousand men to conceal themselves so as to be invisible from the city. It would appear (ver. 17) that the people of Bethel had left their own village and gone into Ai. Bethel, as we have said, was situated higher up; in fact, it was on the very ridge of the plateau of Western Palestine. It must have been but a little place, and its people seem to have deemed it better to join those of Ai, knowing that if the Israelites were repulsed from the lower city, the upper was safe.