C. F. Keil and Franz Delitzsch on Judges 6:39-40

Jdg 6:39-40

But as this sign was not quite a certain one, since wool generally attracts the dew, even when other objects remain dry, Gideon ventured to solicit the grace of God to grant him another sign with the fleece, - namely, that the fleece might remain dry, and the ground all round be wet with dew. And God granted him this request also. Gideon’s prayer for a sign did not arise from want of faith in the divine assurance of a victory, but sprang from the weakness of the flesh, which crippled the strength of the spirit’s faith, and often made the servants of God so anxious and despondent, that God had to come to the relief of their weakness by the manifestation of His miraculous power. Gideon knew himself and his own strength, and was well aware that his human strength was not sufficient for the conquest of the foe. But as the Lord had promised him His aid, he wished to make sure of that aid through the desired sign.“From all these things, the fact that he had seen and heard the angel of Jehovah, and that he had been taught by fire out of the rock, by the disappearance of the angel, by the vision of the night, and by the words addressed to him there, Gideon did indeed believe that God both could and would deliver Israel through his instrumentality; but this faith was not placed above or away from the conflict of the flesh by which it was tested. And it is not strange that it rose to its greatest height when the work of deliverance was about to be performed. Wherefore Gideon with his faith sought for a sign from God against the more vehement struggle of the flesh, in order that his faith might be the more confirmed, and might resist the opposing flesh with the great force. And this petition for a sign was combined with prayers for the strengthening of his faith.” - Seb. Schmidt.

And “the simple fact that such a man could obtain the most daring victory was to be a special glorification of God” (O. v. Gerlach). The sign itself was to manifest the strength of the divine assistance to his weakness of faith. Dew in the Scriptures is a symbol of the beneficent power of God, which quickens, revives, and invigorates the objects of nature, when they have been parched by the burning heat of the sun’s rays. The first sign was to be a pledge to him of the visible and tangible blessing of the Lord upon His people, the proof that He would grant them power over their mighty foes by whom Israel was then oppressed. The woollen fleece represented the nation of Israel in its condition at that time, when God had given power to the foe that was devastating its land, and had withdrawn His blessing from Israel. The moistening of the fleece with the dew of heaven whilst the land all round continued dry, was a sign that the Lord God would once more give strength to His people from on high, and withdraw it from the nations of the earth. Hence the second sign acquires the more general signification, “that the Lord manifested himself even in the weakness and forsaken condition of His people, while the nations were flourishing all around” (O. v. Gerl.); and when so explained, it served to confirm and strengthen the first, inasmuch as it contained the comforting assurance for all times, that the Lord has not forsaken His church, even when it cannot discern and trace His beneficent influence, but rules over it and over the nations with His almighty power.