But now let's see why, in the first sign, "dew fell upon the fleece, whereas the ground was dry," and in the second sign, "dew fell upon the ground, while the fleece remained dry," an indication which Gideon accepted as a pledge that the Lord would save Israel through his hand. The rationale for this mystery is to be seen in what I remember from one of our preceding books, which characterized the people of Israel as a "fleece," with the surrounding ground being the Gentiles, while the dew that fell "upon the fleece" was the word of God written for this people alone. For only to Israel did the dew of the divine law arrive, whereas all the surrounding nations remained dry, none of them being infused with the moisture of divine locution. In the second sign, however, where he asked that the dew fall on the ground and that the fleece remain dry, a completely different rationale can be observed. We should see this entire people, who were gathered together from nations around the world, now having within themselves the divine dew; see them infused with the dew of Moses, irrigated by the word of the prophets; see them green from evangelical and apostolic water. The fleece, however, that is, the Jewish people, suffers aridity and dryness in the word of God, according to which it is written: "The children of Israel will be for a long time without king, without prince, without prophet; they will have no altar, no victim, no sacrifice." You can see how they remain arid, how they are stricken with drought of the word of God.… Even the seventy-first psalm, as I have often discussed with them, moves me to this conclusion because, when it describes the advent of Christ, it foretells his coming as rain on a fleece and as showers on the earth. Here in Judges a fleece is mentioned and in the psalm, also, "fleece" is the word chosen. For he will "descend like rain," it says, "on a fleece." He descends, therefore, on that fleece of the people of circumcision and "like showers upon the earth," meaning that our Lord Jesus Christ descends on the remainder of the earth, dripping upon us and bringing the "dew of heaven" to us Gentiles also, that we too may drink who were on the previously arid surrounding land.
Source: HOMILIES ON JUDGES 8.4