21. desire--of your own accord madly courting that which must condemn and ruin you.
      do ye not hear--do ye not consider the mystic sense of Moses' words? [GROTIUS]. The law itself sends you away from itself to Christ [ESTIUS]. After having sufficiently maintained his point by argument, the apostle confirms and illustrates it by an inspired allegorical exposition of historical facts, containing in them general laws and types. Perhaps his reason for using allegory was to confute the Judaizers with their own weapons: subtle, mystical, allegorical interpretations, unauthorized by the Spirit, were their favorite arguments, as of the Rabbins in the synagogues. Compare the Jerusalem Talmud [Tractatu Succa, cap. Hechalil]. Paul meets them with an allegorical exposition, not the work of fancy, but sanctioned by the Holy Spirit. History, if properly understood contains in its complicated phenomena, simple and continually recurring divine laws. The history of the elect people, like their legal ordinances, had, besides the literal, a typical meaning (compare 1Co 10:1-4; 15:45, 47; Re 11:8). Just as the extra-ordinarily-born Isaac, the gift of grace according to promise, supplanted, beyond all human calculations, the naturally-born Ishmael, so the new theocratic race, the spiritual seed of Abraham by promise, the Gentile, as well as Jewish believers, were about to take the place of the natural seed, who had imagined that to them exclusively belonged the kingdom of God.

JFB.